Night Owl 6/Night Owl's Shareware - PDSI-006 - Night Owl Corp (1990).iso/038a/qbatb503.zip/TOOLBOX.DOC

Text File | 1991-07-06 | 121KB | 3,059 lines

            Assembly-Language Toolbox for QuickBASIC
            ────────────────────────────────────────
                       By Christy Gemmell

The Assembly-Language Toolbox started life, four years ago, as a simple
collection of useful routines for adding zip to my QuickBASIC programs.
They weren't just pretty faces however. In order to qualify, the Toolbox
routines had to work reliably with real-life commercial applications, the
ones on which my living depended. This made for pretty tough testing, but
those which did survive were, in consequence, fast, robust and, above all,
able to do the job. They are, in fact, doing so in Accountants and Stock-
broker's offices, all over my native Great Britain.

A colleague uploaded a copy of the Toolbox onto a local BBS (Electronic
Bulletin Board) and suddenly I started getting letters and phone calls
from complete strangers asking for a copy of the latest version. Nearly
everyone who called had suggestions of their own, remarking; "You know, if
only the Toolbox had this, it would be really good...".

Wherever practicable, the good ideas (and some were brilliant) were turned
into assembler code and added to the collection. Almost before I realised
what was happening, the Assembly-Language Toolbox was on the Shareware
circuit and being used by programmers in Europe, the USA, Canada,
Australia and Japan. By December 1990 it had gone through four 'official'
releases and a dozen or more unofficial ones.

Release Five comes in two flavours; one for QuickBASIC 4 and the other for
Microsoft's BASIC 7 Professional Development System. The QB4 version
covers QuickBASIC 4.0, 4.5 and BASIC 6 while the PDS version is compatible
with BASIC 7, 7.1 and Extended QuickBASIC (QBX). In either version the
routines are provided both as stand-alone libraries and as Quick Libraries
for use in the programming environment.

Using the Toolbox is easy. All the routines are written to look like
standard QuickBASIC SUB programs and FUNCTION procedures. All you have to
do is choose the ones you want to use in your current program and paste
the appropriate DECLARE statements (a full set is provided) into the
source code. If you need to output large quantities of text to the screen
at high speed, for example, just copy the following line from TOOLBOX.DEF.

DECLARE SUB FastPrint (BYVAL Row%, BYVAL Col%, Text$, BYVAL Attribute%)

Then, if you are running in the QuickBASIC environment, you should load
the Quick Library with the command:

    QB yourprog.bas /L toolbox.qlb

Thereafter you can call FastPrint, exactly as you would any other
QuickBASIC SUB program, for example like this:

    FastPrint 25, 34, "Hello World!", 48

which will print 'Hello World!' in the middle of the 25th screen row
displaying it in black characters on a cyan background (if you have a
colour monitor). Notice that, since a DECLARE statement has been used, you
don't need to place parentheses around the argument list and that even the
CALL statement is unneccessary. Used in this way, Toolbox routines become
actual extensions to the QuickBASIC language.

The same DECLARE statements can still be used when you compile your
programs from the DOS command line. In this case, however, you must link
the compiled program to TOOLBOX.LIB, the stand-alone library, with
something like this:

    LINK yourprog,,,toolbox.lib;

The QuickBASIC Linker will only extract, from TOOLBOX.LIB, those modules
which are explicitly named by DECLARE statements in the source file. This
ensures that your programs are not burdened with unneccessary code.

Toolbox routines do not require the BASIC runtime module to be present.
You can use them to produce completely stand-alone application programs
which can be distributed commercially.

As its name implies, the core routines in the Assembly-Language Toolbox
are written in pure Intel 80x86 assembler. Because of this they are small,
efficient and blindingly fast. Moreover, since any internal variables are
stored in a routine's own code segment, your program does not have to
share any of it's precious data space with the library.

Christy Gemmell                                                 June 1991

──────────────────────────────────────────────────────────────────────────

The ShareWare version of the Assembly-Language Toolbox for QuickBASIC is
provided, free of charge, to any QuickBASIC programmer who can find a use
for it. You are encouraged to copy it, upload it to Electronic Bulletin
Boards or pass it on to friends, provided only that you make no charge for
doing so and that all the files on the disk are preserved intact. You may
freely include Toolbox routines in your own programs, both for private use
and for commercial distribution, without payment to the author.

The Professional version of the Toolbox, available to Registered Users,
comes complete with all the source code, object modules for building your
own custom libraries and many additional features. Registration also
entitles you to a free upgrade to Release 6 of the Toolbox, when it
becomes available, and to subsequent releases at a greatly reduced price.
Full Hotline support is also included, at no extra charge.

Also available is the Mixed-Language Toolbox for QuickBASIC - a collection
of high-level routines which interface with the Assembly-Language Toolbox
to produce a set of sophisticated mini-applications. The BarMenu and
VerMenu modules, for example, can be used to give your programs a full-
featured point-and-shoot menuing system, similar to the one built into the
QuickBASIC programming environment. Once again, the source code for all
mixed-language routines is provided so that you can tailor them to your
exact requirements.

─────Registration and Support──────────────────────────────────────────────

U.K. and Europe:        £30.00 (including postage and packing)

Christy Gemmell         Singular Software
                        22 Peake Road, Northfields,
                        Leicester LE4 7DN
                        United Kingdom

                Tel:    [phone]

U.S.A. and Canada:      $47.50 (Including shipping)

James J. Kreyling       CPC Consulting Company
                        1217 Crescent Dive
                        Smithfield, Va. 23430
                        U.S.A.

                Tel:    [phone]
or from Club-PC BBS:    (804)-357-0357 (8-N-1)

Note:   When ordering the Toolbox please specify if for QuickBASIC 4.5
        or BASIC 7 PDS and the floppy disk format you require.

─────About the author─────────────────────────────────────────────────────

Christy Gemmell, the author of this package, is also major author of the
definitive textbook on QuickBASIC programming, the QuickBASIC BIBLE, which
is published by Microsoft Press, in association with the Waite Group, at
£24.95 ($27.95 US) ISBN 1-55615-262-0. Selected as Computer Book of the
Month by Jerry Pournelle in the March 1991 issue of BYTE, its thousand
pages are packed with information, tips and example programs which you
wont find anywhere else.  Look out for it in your local bookstore.

The Assembly-Language Toolbox for QuickBASIC is used by thousands of
programmers in Great Britain, Europe, the USA and Canada, Australasia and
Japan, to build fast and powerful QuickBASIC programs. It has been shown
at COMDEX and was featured in the November 1990 issue of BYTE magazine.

───────────────────────────────────────────────────────────────────────

                TOOLBOX FUNCTIONS AND PROCEDURES

This is a full, alphabetical, listing of the routines in the Assembly
Language Toolbox which can be called directly by QuickBASIC programs>


ATTRIB

This function returns the directory attributes of the specified file.

DECLARE FUNCTION Attrib% (FileSpec$)

FileSpec$ is the name of the file whose directory entry is to be tested.
You should include the full pathname (including drive letter if necessary)
if the file is not in the current directory.

The returned attribute value is bit-encoded as follows:

   Bit     Meaning (if set)
─────────────────────────────────────────────────────
    0      Read-only     (file is Read/Write if zero)
    1      Hidden
    2      System
    3      Volume label
    4      Subdirectory
    5      Archive
    6      Not used
    7      Shareable     (Novell Networks only)
─────────────────────────────────────────────────────

The ToolBox procedures; HIDE, SECURE and SHARE (see below) can be used to
modify the attributes of a file.


ATTRIBUTE

Converts standard QuickBASIC foreground and background COLOR values into
their equivalent display attribute number.

DECLARE FUNCTION Attribute% (BYVAL Fore%, BYVAL Back%)

The Assembly-Language Toolbox provides several routines which allow  your
QuickBASIC programs to write text directly to the display with an
attribute which you supply. For an explanation of display attributes, see
the topic file COLOURS.HLP supplied with the Assembly-Language Toolbox
demonstration program.


BACKFILL

This procedure changes the display attributes of the characters contained
within the screen rectangle you specify, without overwriting the text
itself.

DECLARE SUB BackFill (BYVAL R%, BYVAL C%, BYVAL H%, BYVAL W%, BYVAL A%)

R% = Top-left row of the rectangle to be coloured.
C% = Top-left column of the rectangle.
H% = Height of the rectangle in rows.
W% = Width of the rectangle in columns.
A% = Display attribute to use for colouring.


CAPSLOCK

Toggles CAPS LOCK on or off or, alternatively, reads the current CAPS LOCK
key setting.

DECLARE FUNCTION CapsLock% (BYVAL Switch%)

Switch% = 0  Turns CAPS LOCK off
        = 1  Turns CAPS LOCK on

Any other value just returns the current CAPS status as a logical value
where -1 (TRUE) means that CAPS LOCK is on and 0 (FALSE) means that CAPS
LOCK is off.


CGACOPY

Copies a CGA screen to or from a user-supplied string.

DECLARE SUB CgaCopy (BYVAL Switch%, Buffer$)

SWITCH%     Direction of copy   0 = copy screen to string
                                1 = copy string to screen

BUFFER$     String variable to hold the screen image, must be at least
            16384 characters long or the call will fail.

Note:       If you are using QuickBASIC 4 or 4.5, do not pass a fixed-
            length string to this routine. Only variable-length strings
            will work safely.

The QuickBASIC PCOPY statement is very useful for storing screen pages in
memory, so that they can be kept out of sight until needed. Unfortunately
it only works in text modes or, on computers with EGA or VGA video cards,
in SCREEN modes 7 to 12. This routine, on the other hand, works only in
the CGA display modes (SCREENs 1 and 2), it provides a useful alternative
to the PCOPY statement for use with medium-resolution screens.

See also MCGACOPY for a version that can be used with SCREEN 13 displays.


CGASCROLL

Scrolls a rectangular portion of a SCREEN 1 (320 x 200 4-colour) display
four pixels to the left or to the right, wrapping the pixels which are
scrolled out at the end round to the beginning again.

DECLARE SUB CgaScroll (BYVAL xLoc%, BYVAL yLoc%, BYVAL xPixels%,_
                       BYVAL yPixels%, BYVAL Direction%)

XLOC%       The horizontal (X) co-ordinate of the top-left corner of
            the rectangle to be scrolled.

YLOC%       The vertical (Y) co-ordinate of the top-left corner of
            the rectangle to be scrolled.

XPIXELS%    The width (in pixels) of the rectangle to be scrolled.

YPIXELS%    The height (in pixels) of the rectangle to be scrolled.

DIRECTION%  The direction in which the rectangle contents are to be
            scrolled (0 = Left, 1 = Right).

Co-ordinates are in the ranges:  X >= 0 <= 319, Y >= 0 <= 199

X co-ordinates are aligned to the nearest byte (1 byte = 4 pixels).


CGATEXT

Writes characters to the screen in the 320 x 200 4-colour graphics mode.

DECLARE SUB CgaText (BYVAL xLoc%, BYVAL yLoc%, Text$,_
                     BYVAL Attr%, BYVAL Scale%)

This routine provides a convenient way of displaying text in SCREEN 1
without having to bother about loading external font files. It uses the
standard ROM-BIOS character definition tables built into your display
adaptor, but allows you to scale them up to eight times normal size and to
specify any combination of foreground and background colours.

XLOC%       The horizontal co-ordinate of the top left hand pixel
            from which the text will begin (0 - 319)

YLOC%       The vertical co-ordinate of the top left hand pixel
            from which the text will begin (0 - 199)

TEXT$       The string of text to be displayed (up to 63 characters).

ATTR%       The colour (or display attribute in monochrome modes) to
            be given to the text. This is calculated by the formula:

            Colour% = (Background% * 256) + Foreground%

            Foreground and Background values are in the range 0 - 3

SCALE%      The character size of the text to be displayed. This ranges
            from 1 to 8, where 1 is standard 40-column text and where 8
            multiplies the character size by eight on both the horizontal
            and vertical axes.

CGATEXT can handle both byte-aligned and non byte-aligned characters. The
x, y co-ordinates you supply do not need to correspond to a row, column
character cell in SCREEN 0, the alphanumeric mode. The complete ASCII set
is supported, but to display foreign symbols and box-drawing characters on
a CGA adaptor you must have the DOS GRAFTABL utility loaded.

Since CGATEXT does not support clipping, to ensure a clean display you
must ensure that the text to be output fits within the current screen
boundaries.

See also VGATEXT for displaying characters in SCREENs 7-12 and MCGATEXT
for displaying characters in SCREEN 13.


CIPHER

This routine requires that you supply two strings of characters. The first
is the text to be encrypted, and the second is one or more keywords which
are used to encipher the text. Thereafter, the text cannot be decrypted
until you supply the same key string again.

DECLARE SUB Cipher (Text$, KeyWord$)

The encryption algorithm XORs (eXclusive ORs) the key string with string
to be encrypted. This allows you to reverse the procedure and decrypt the
text, simply by calling the routine a second time.

See the source code for DEMON.BAS, the ToolBox demonstration program, for
an example using CIPHER.


CLEAREND

Blank spaces of the display attribute specified are printed, starting at
the current cursor position and continuing to the end of the line or,
optionally, to the end of the screen.

DECLARE SUB ClearEnd (BYVAL Switch%, BYVAL Attr%)

Switch%   0 = clear to the end of the line.
          1 = clear to the end of the screen.

Attr%     display attribute (1 - 255). If zero is specified then the
          attribute of the character under the cursor is used.

Example:  ClearEnd 1, 0

Clears from the current cursor position to the bottom of the screen. The
area cleared takes the background colour of the character under the
cursor. The cursor, itself, is not updated.


CPU

This function checks to see what type of microprocessor is installed in
the computer in which the current program is running.

No calling parameters are required.

DECLARE FUNCTION Cpu% ()

The following processors can be identified by their return values :

 86 = Intel 8086          88 = Intel 8088         188 = Intel 80188
186 = Intel 80186        286 = Intel 80286        386 = Intel 80386
-86 = Intel 80C86        -88 = Intel 80C88         20 = NEC   V20
 30 = NEC   V30

486 = Intel 80486  included but not yet tested (lend us yours?).

This function is provided mainly for interest, although it can be used as
an indication of how long a particular task will take to run. All of the
Toolbox routines, in fact, are processor-independent and can be used on
all types of IBM-PC, AT, PS/2 and compatible machines


CURTAINS

This routine clears the display screen to the background colour specified
by Attribute%. It differs from CLS in that the blanked-out area expands
from a series of columns, giving the effect of a set of louvered blinds or
curtains being closed. The Speed% parameter controls how quickly the
routine runs, larger values making the curtains close more slowly.

DECLARE SUB Curtains (BYVAL Speed%, BYVAL Attribute%)

Try this example for a fancy effect:

FOR I% = 255 TO 0 STEP -16: Curtains 40, I%: NEXT

This procedure calls the DELAY routine (see below). This ensures that the
speed value you specify will produce the same result on computers with any
type of processor or clock speed.


DAYNUMBER

Convert a date in the form DD/MM/YYYY to a long integer. The values
returned are valid with dates in the range 1/3/1900 - 31/12/2099.

DECLARE FUNCTION DayNumber& (BYVAL Day%, BYVAL Month%, BYVAL Year%)

See the INTERVAL function (below) for a method of calculating the number
of days between two Julian dates.


DELAY

This procedure is like the QuickBASIC SLEEP statement, except that it
allows you to specify an interval in milliseconds instead of just whole
seconds. The delay will be exactly the same on a 4.77 MHz original PC as
it would be on the latest 33-MHz 80486 machine.

DECLARE SUB Delay (BYVAL MilliSeconds%)

See the PAUSE routine (below) for a similar procedure which allows you to
specify a delay in PC clock ticks.


DISABLEPRTSC

This routine simply sets the Print Screen Busy flag at low-memory address
0040:0100 (Hex) so that any requests for the screen to be printed are
ignored. Use this to prevent a careless operator from hanging-up the
program by pressing <Prt Scrn> when the printer is off-line.

No calling parameters are required.

DECLARE SUB DisablePrtSc ()

Don't forget to use ENABLEPRTSC (see below) to re-enable this key
otherwise it will remain disabled even after your program ends.


DISKREADY

Tests if there is readable media in the floppy diskette drive specified.

DRIVE% is the number of the diskette drive to be tested and is a value
between 0 and 3, where 0 = A:, 1 = B:, etc.

DECLARE FUNCTION DiskReady% (BYVAL Drive%)

This function returns -1 (logical TRUE) if a readable diskette is in the
drive, and zero (logical FALSE) if unable to read from the drive.

Note:       DISKREADY only tests if the drive can be read from. It will
            not detect if the diskette in the drive is write-protected.


DISPLAYMODE

Reads the current video display mode using the IBM ROM-BIOS numbering
system.

DECLARE FUNCTION DisplayMode% ()

No calling parameters are required. Depending on the type of display
adaptor installed, the function may return one of the following values:

Mode    Resolution      Mode     Colours    Remarks
─────────────────────────────────────────────────────────────────────
  0     40 x 25         text        16      No colour burst
  1     40 x 25         text        16
  2     80 x 25         text        16      No colour burst
  3     80 x 25         text        16
  4     320 x 200       graphics     4
  5     320 x 200       graphics     4      No colour burst
  6     640 x 200       graphics     2
  7     80 x 25         text         2      Monochrome display only
  8     160 x 200       graphics    16      PCjr & Tandy 1000 only
  9     320 x 200       graphics    16      PCjr & Tandy 1000 only
 10     640 x 200       graphics     4      PCjr & Tandy 1000 only
 13     320 x 200       graphics    16      EGA & VGA
 14     640 x 200       graphics    16      EGA & VGA
 15     640 x 350       graphics     2      Monochrome EGA & VGA
 16     640 x 350       graphics    16      EGA & VGA
 17     640 x 480       graphics     2      VGA only
 18     640 x 480       graphics    16      VGA only
 19     320 x 200       graphics   256      VGA & MCGA
─────────────────────────────────────────────────────────────────────

The SCREENMODE function (see below) can be used to return the equivalent
QuickBASIC SCREEN number.


DISPLAYPAGE

All video cards except the Monochrome Display Adaptor (MDA) are capable of
switching between two or more pages of display memory. This function
returns the number of the active video page, use the QuickBASIC SCREEN
statement to select the page you require.

No calling parameters are required.

DECLARE FUNCTION DisplayPage% ()

The page number returned can be a value between 0 and 7, depending upon
the current video mode and the amount of display memory installed.

Note:       all Toolbox routines which write directly to the screen will
            automatically detect and send their output to the currently
            active display page.


DWPRINT

Sends the text supplied, to the printer, as a string of double-width
characters. Output begins at the current print position and can,
optionally, append a carriage-return/linefeed to take the print head to
the beginning of a new line when finished.

DECLARE SUB DwPrint (BYVAL Printer%, Buffer$, BYVAL NewLine%)

Arguments:  Printer%    the parallel port output is to be sent to
                        (1 = LPT1:, 2 = LPT2:, etc.).
            Buffer$     the string of text to be printed.
            NewLine%    set this to a non-zero value if you want
                        to move to a new line after printing.

The routine restores the previous print style or font before it returns
and does not effect subsequent output to the printer, using the QuickBASIC
LPRINT or PRINT # statements.

Note:       The version of this routine stored in the Toolbox
            library is for EPSON compatible printers. If you have
            an IBM graphics printer or ProPrinter, then you should
            rebuild your libraries, using either the PRINTIBM.OBJ
            or PRINTPRO.OBJ object module in place of PRINTEPS.OBJ.


EMPRINT

Sends the text supplied, to the printer, as a string of emphasised
characters. Output begins at the current print position and can,
optionally, append a carriage-return/linefeed to take the print head to
the beginning of a new line when finished.

DECLARE SUB EmPrint (BYVAL Printer%, Buffer$, BYVAL NewLine%)

Arguments:  Printer%    the parallel port output is to be sent to
                        (1 = LPT1:, 2 = LPT2:, etc.).
            Buffer$     the string of text to be printed.
            NewLine%    set this to a non-zero value if you want
                        to move to a new line after printing.

The routine restores the previous print style or font before it returns
and does not effect subsequent output to the printer, using the QuickBASIC
LPRINT or PRINT # statements.

Note:       The version of this routine stored in the Toolbox
            library is for EPSON compatible printers. If you have
            an IBM graphics printer or ProPrinter, then you should
            rebuild your libraries, using either the PRINTIBM.OBJ
            or PRINTPRO.OBJ object module in place of PRINTEPS.OBJ.


EMSERROR

Returns the code number of the last error which occurred during a
call to the Expanded Memory Manager. If zero is returned, then no
errors have occurred.

No calling parameters are required.

DECLARE FUNCTION EmsError% ()

Here is a list of possible error codes and their meanings:

128  Internal error in EMM software     146  Source and target overlap
129  Malfunction in EMS hardware        147  Illegal region length
130  Memory manager busy                148  Region overlap
131  Invalid handle                     149  Offset outside logical page
132  Function not defined               150  Region length > 1MB
133  No more handles available          151  Cannot exchange overlap
134  Error in mapping context           152  Memory types undefined
135  Not enough pages exist             153  Not used
136  Not enough pages available         154  ARS not supported
137  Cannot allocate zero pages         155  ARS currently allocated
138  Page not allocated to handle       156  ARS not zero
139  Illegal physical page number       157  ARS not allocated
140  Save state area full               158  DMA channels not supported
141  Save of mapping context failed     159  Illegal DMA channel
142  Restore of mapping context failed  160  No handle for this name
143  Subfunction parameter not defined  161  Name already exists
144  Attribute type not defined         162  Memory address wrap
145  Feature not supported              163  Invalid pointer

250  EMM not installed*                 251  LIM 4.0 required*

*    Toolbox error codes.

The descriptions are, of necessity, abbreviated. For more information
consult your EMS hardware manual or see:

Advanced MS-DOS Programming     by David Duncan     Microsoft Press


EMSFRAME

Returns the segment address of the EMS page frame.

No calling parameters are required.

DECLARE FUNCTION EmsFrame% ()

The Page Frame is the area of conventional memory into which logical
expanded memory pages are mapped. Under LIM 3.2 it is a contiguous
block of 64RAM, divided into four 16K physical pages, located some-
where between segments A000 and F000 Hex, but LIM 4.0 allows you to
reserve additional 16K pages, wherever available memory exists. In
either system you can rely on 4 consecutive 16K pages and this
function returns a pointer to the first of them.


EMSGET

Copies up to 64KB of data from expanded memory, starting at the
logical page supplied, to an address in conventional memory.

DECLARE SUB EmsGet (BYVAL Segment%, BYVAL Offset%, BYVAL Length%,_
                    BYVAL Page%, BYVAL Handle%, Done%)

Arguments:  Segment%  = segment address of target block to which
                        data should be copied.
            Offset%   = offset address, within target segment, to
                        which data should be copied.
            Length%   = length, in bytes (up to 64KB), of data to
                        be copied.
            Page%     = logical EMS page holding the beginning of
                        the data. If the block of data is bigger
                        than 16KB, then copying will continue from
                        subsequent pages until all the data has
                        been moved.
            Handle%   = the EMS handle to which the page(s) have
                        been allocated. This should be obtained by
                        a previous call to the EMSRESERVE procedure
                        (see below).
            Done%     = a flag to hold the result of the operation.
                        If the data was copied successfully, it is
                        set to -1 (logical TRUE) on return. If zero
                        (logical FALSE) is returned, the data was
                        not copied successfully. In this case, you
                        should make a call to the EMSERROR function
                        to find out why.

If the target structure, to which the data is to be copied, is an
array, you should specify its address by supplying the VARSEG and
VARPTR of the first element. Be sure, however, that you do not copy
a block of data bigger than the array size, otherwise you may
overwrite other variables, probably with disastrous results.

See the EMSPUT procedure (below) for a means of copying data into
logical expanded memory pages.


EMSMAP

Map a logical expanded memory page to a physical page in the EMS
Page Frame, making it accessible to your program.

DECLARE SUB EmsMap (BYVAL Handle%, Physical%, Logical%)

Arguments:  Handle%   = the EMS handle to which the logical page has
                        been allocated. This will have been obtained
                        by a previous call to the EMSRESERVE routine
                        (see below).
            Physical% = the number of the physical page to map
                        (in the range 1 to 4).
            Logical%  = the number of the logical page to be mapped
                        (in the range from 1 to the number of pages
                        allocated to Handle%).

For most applications, the EMSGET and EMSPUT procedures will be more
useful, since they perform all the necessary mapping for you while
moving data to and from expanded memory. If, however, you need to
manipulate small quantities of data in expanded memory, use this
routine to switch the relevant page into conventional memory, and
the FARPEEK and FARPOKE utilities (see below) to examine or change
the data itself.


EMSOWNED

Returns the number of logical pages of EMS memory that have been
allocated to the handle specified.

DECLARE FUNCTION EmsOwned% (BYVAL Handle%)


EMSPAGES

Returns either the total number of EMS pages in the system, or the
total number of free (unallocated) pages.

DECLARE FUNCTION EmsPages% (BYVAL Switch%)

Argument:   Switch% = 1  return number of unallocated pages.
                      0  return total number of pages in system.


EMSPRESENT

Tests whether the Expanded Memory System driver has been installed

No calling parameters are required.

DECLARE FUNCTION EmsPresent% ()

Returns:    -1  (logical TRUE) if EMS driver is installed.
             0  (logical FALSE) if EMS driver is not installed.

Note:       This function just checks that the EMS driver is in
            memory and that the EMS interrupt vector is directed
            to it, it does not test if the driver is active. Use
            the EMSVERSION function (see below) to test this. If
            the driver responds to that function, it can be safely
            assumed to be active.


EMSPUT

Copies up to 64KB of data to expanded memory, starting at the
logical page supplied, from an address in conventional memory.

DECLARE SUB EmsPut (BYVAL Segment%, BYVAL Offset%, BYVAL Length%,_
                    BYVAL Page%, BYVAL Handle%, Done%)

Arguments:  Segment%  = segment address of source block from which
                        data is to be copied.
            Offset%   = offset address, within target segment, from
                        which data is to be be copied.
            Length%   = length, in bytes (up to 64KB), of data to
                        be copied to expanded memory.
            Page%     = logical EMS page to hold the beginning of
                        the data. If the block of data is bigger
                        than 16KB, then copying will continue onto
                        subsequent pages until all the data has
                        been moved.
            Handle%   = the EMS handle to which the page(s) have
                        been allocated. This should be obtained by
                        a previous call to the EMSRESERVE procedure
                        (see below).
            Done%     = a flag to hold the result of the operation.
                        If the data is copied successfully, it will
                        be set to -1 (logical TRUE) on return. If
                        zero (logical FALSE) is returned, the data
                        was not copied successfully. In this case,
                        you should make a call to the EMSERROR
                        function to find out why.

If the source structure, from which the data is to be copied, is an
array, you should specify its address by supplying the VARSEG and
VARPTR of the first element. You can also copy data from absolute
addresses in memory to EMS, to copy the contents of the text screen,
for example, to EMS logical page 2, use the command:

    EmsPut &HB800, 0, 4000, 3, Handle%, Done%

This assumes that your computer has a colour monitor. If you have a
monochrome display, substitute &HB000 for the segment address.

See the EMSGET procedure (above) for a means of retrieving data from
extended memory.


EMSRELEASE

Free-up all the pages previously allocated to this handle, and make
them available to other processes.

DECLARE SUB EmsRelease (BYVAL Handle%)

You should release all the EMS pages which have been allocated to
handles owned by your program, before the program terminates. If
this is not done, these pages will not be available to subsequent
programs which may start up and will remain locked until the system
is rebooted.


EMSREQUEST

Asks for one or more logical pages of expanded memory to be made
available to your program.

DECLARE SUB EmsRequest (BYVAL Pages%, Handle%)

Arguments:  Pages%  = number of EMS pages to reserve.

            Handle% = if successful, this variable will hold the
                      number of the EMS handle which controls the
                      allocated pages. If unsuccessful, Handle%
                      will be set to zero on return, in which case
                      you should call the EMSERROR function (above)
                      to see what went wrong.

You must use this handle in all subsequent calls to the Expanded
Memory Manager which refer to these particular pages.

Before calling this procedure, it is a good idea to make a call to
the EMSPAGES function (see above) to see how many pages are free.


EMSRESIZE

Changes the number of pages allocated to an EMS handle.

DECLARE SUB EmsReSize (BYVAL Handle%, Pages%)

Arguments:  Handle% = a valid EMS handle to which logical expanded
                      memory pages have already been allocated.

            Pages%  = the new number of pages to be allocated to
                      this handle.

On return, Pages% will hold the actual number of pages that are
now allocated to the handle. If this is different from the number
of pages requested, then an error has occurred and you should call
the EMSERROR function (see above) to check what happened.

You can request a number of pages less than or greater than the
number previously allocated to the handle.

Note:       This facility is only available with LIM 4.0 EMS and
            above.


EMSVERSION

Returns the LIM version number of the Expanded Memory Manager.

No calling parameters are required.

DECLARE FUNCTION EmsVersion% ()

The number returned is a decimal integer where 32 represents LIM 3.2
and 40 represents LIM 4.0. If zero is returned, then an error has
occurred and you should call the EMSERROR function (see above) to
find out what happened. Use the EMSPRESENT function (also above) to
test that the EMM driver has, in fact, been installed.


ENABLEPRTSC

This routine clears the Busy flag at low-memory address 0040:0100 (Hex) so
that print-screen requests can be executed. Use it to cancel the effect of
the DISABLEPRTSC procedure (above).

No calling parameters are required.

DECLARE SUB EnablePrtSc ()


ENPRINT

Sends the text supplied, to the printer, as a string of enhanced
characters. Output begins at the current print position and can,
optionally, append a carriage-return/linefeed to take the print head to
the beginning of a new line when finished.

DECLARE SUB EnPrint (BYVAL Printer%, Buffer$, BYVAL NewLine%)

Arguments:  Printer%    the parallel port output is to be sent to
                        (1 = LPT1:, 2 = LPT2:, etc.).
            Buffer$     the string of text to be printed.
            NewLine%    set this to a non-zero value if you want
                        to move to a new line after printing.

The routine restores the previous print style or font before it returns
and does not effect subsequent output to the printer, using the QuickBASIC
LPRINT or PRINT # statements.

Note:       The version of this routine stored in the Toolbox
            library is for EPSON compatible printers. If you have
            an IBM graphics printer or ProPrinter, then you should
            rebuild your libraries, using either the PRINTIBM.OBJ
            or PRINTPRO.OBJ object module in place of PRINTEPS.OBJ.


EXPLODE

Clear a screen rectangle explosively. This as an alternative to the
SCROLL routine listed below.

DECLARE SUB Explode (BYVAL Y1%, BYVAL X1%, BYVAL Y2%, BYVAL X2%,_
                     BYVAL Attribute%, BYVAL Speed%)

Arguments:  Y1%         =  Upper-left row of rectangle to be cleared
            X1%         =  Upper-left column of rectangle
            Y2%         =  Lower-right row of rectangle
            X2%         =  Lower-right column of rectangle
            Attribute%  =  Display attribute or colour that rectangle
                           should be cleared to
            Speed%      =  Speed (in milliseconds) of explosion.

The panel is cleared, starting at the centre point, and progressively
moving outwards until the defined borders are reached. This gives the
impression of the clear area exploding onto the screen.

This routine is called, internally, by the POPUP window function (see
below) whenever Zoom is specified.


FARPEEK

Reads a byte of data from anywhere in conventional memory.

DECLARE FUNCTION FarPeek% (BYVAL Segment&, BYVAL Offset&)

Arguments:  Segment&  = address of memory segment containing the byte
                        to be read.
            Offset&   = offset address, within the segment of the
                        byte to be read.

Returns:    The contents of the byte specified as an integer value
            in the range 0 to 255.

Note:       parameters are passed as LONG integers to save you the
            hassle of having to convert argument values over 32767
            to negative signed integers. Do not use values greater
            than 65535, however, or the most significant word will
            be ignored and the address converted to Modulus 65536.

Using QuickBASIC's PEEK function to examine data which lies outside
of DGROUP is a pain. You also have to use DEF SEG to set the segment
required and then to reset it afterwards. This function allows you to
read bytes, directly, from anywhere in the 1 megabyte of addressable
RAM space your computer contains.

The FARPOKE procedure (below) complements FARPEEK by allowing you to
write a byte of data anywhere in the 1MB addressable PC workspace.

See also PEEKWORD and POKEWORD which allow you to read from and write
to memory, two bytes at a time.

Note:       If you have an Intel 286, 386 or 486-based computer with
            the Microsoft HIMEM.SYS driver loaded, you can even use
            FARPEEK to read from the first 64KB of Extended Memory.
            Setting the segment to &HFFFF and an offset in the range
            &H10 to &HFFFF allows you access up to 65520 bytes of
            memory ABOVE the normal 1MB limit.


FARPOKE

Writes a byte of data to anywhere in conventional memory.

DECLARE SUB FarPoke (BYVAL Segment&, BYVAL Offset&, BYVAL Byte%)

Arguments:  Segment&  = address of memory segment containing the byte
                        to be written to
            Offset&   = offset address, within the segment of the
                        byte to be written.
            Byte%     = the value (0 to 255) to be written to the
                        specified byte.

Note:       addresses are passed as LONG integers to save you the
            hassle of having to convert argument values over 32767
            to negative signed integers. Do not use values greater
            than 65535, however, or the most significant word will
            be ignored and the address converted to Modulus 65536.

Using QuickBASIC's POKE function to write to memory which is outside
of DGROUP is a pain. You also have to use DEF SEG to set the segment
you want and then to set it back again afterwards. This function lets
you write bytes, directly, anywhere in the 1 megabyte of addressable
RAM space your computer contains.

The FARPEEK procedure (above) complements FARPOKE by allowing you to
read a byte of data from anywhere in the 1MB of addressable memory.

See also PEEKWORD and POKEWORD which allow you to read from and write
to memory, two bytes at a time.


FASTPRINT

This procedure can be used to display a string of text directly to video
memory. It is much  faster than the normal DOS services and does not
update the cursor.

DECLARE SUB FastPrint (BYVAL Row%, BYVAL Col%, Message$, BYVAL Attr%)

Row%        is the row where printing is to start.
Col%        is the column where printing is to start.
Message$    is the string of text to be printed.
Attr%       is the video attribute given to the text.

Row% and Col% follow the QuickBASIC convention of numbering screen rows
and columns with Row = 1, Column = 1 being at the top-left corner of the
display. The maximum value for Row% depends on the capabilities of the
video adaptor installed and is determined by the last WIDTH statement.
Normally it is 25 but may extend to 43 (EGA) or even 50 rows (VGA).
Maximum columns may be either 40 or 80 (the default).

If multiple screen pages are being used, FASTPRINT will correctly identify
the active one and output to the proper video address.


FILEDATE

Gets or sets the date and time of the specified file as is displayed in
directory listings.

DECLARE SUB FileDate (BYVAL Switch%, DateTime$, FileSpec$)

Switch%     if set to a value of 1, changes the date and time of the file
            to the parameters specified in DateTime$. Any other value
            returns the date and time that the file was last written to
            in DateTime$

DateTime$   A string of at least 17 characters in length. If setting the
            date and time of a file, this must be written in a standard
            UK date/time format, ie:

            "DD/MM/YY HH:MM:SS"

            If you are reading the date and time, it is not necessary to
            pre-format the string, as the function will do it for you. The
            string must be of sufficient length to hold the returned date
            and time, however, or the procedure will fail.

FileSpec$   A string holding the pathname of the file to be examined or
            changed. It can include the drive letter and directory path
            were appropriate, but must be an explicit pathname. Wildcard
            characters are not allowed. Maximum length is 64 characters.

The procedure will fail if the file does not exist or is not on the path
specified. Also, since the file is actually opened by the procedure, there
must be at least one free DOS file handle available when you call it.

You cannot change the date and time of a file which has been flagged as
readonly or, on a network, is owned by another program.


FLOPPYDRIVES

This function returns the number of installed diskette drives in the
current computer system.

DECLARE FUNCTION FloppyDrives% ()

No calling parameters are required.


FREESPACE

You must supply the drive number of the diskette or fixed-disk which you
want to test (1 = drive A:, 2 = drive B:, etc). Pass a value of zero to
test the currently-logged or default drive. The amount of free space is
returned in bytes.

DECLARE FUNCTION FreeSpace& (BYVAL DriveNo%)

Note:       The return value will not be reliable if the drive being
            tested has an extended DOS partition which contains more
            than 32MB of free space.


GAMESPORT

This function checks to see if the host computer is fitted with an adaptor
for joysticks or a games paddle.

No calling parameters are required.

DECLARE FUNCTION GamesPort% ()

Returns logical TRUE (-1) if a games adaptor is present or FALSE (0) if no
games adaptor is fitted.


GRAPRINT

This routine simply serves as a function despatcher for the various
graphics text procedures, which can also be called directly. It is
intended to be called from programs which must run under a variety of
video adaptors, transferring control to the proper routine for the current
video mode. The calling program must supply appropriate parameters,
however.

DECLARE SUB GraPrint (BYVAL xLoc%, BYVAL yLoc%, Text$,_
                      BYVAL Attr%, BYVAL Scale%)

GRAPRINT provides a convenient way of displaying text in any of the EGA,
VGA and MCGA graphics modes (SCREENs 7-13) as well as the 320 x 200 pixel
4-colour CGA mode (SCREEN 1) without having to bother about loading
external font files. It uses the standard character definition tables
built into your display adaptor, but allows you to scale them up to eight
times normal size and to specify any combination of foreground and
background colours supported by the current video mode.

XLOC%       The horizontal co-ordinate of the top left hand pixel
            from which the text will begin

YLOC%       The vertical co-ordinate of the top left hand pixel
            from which the text will begin

TEXT$       The string of text to be displayed (up to 63 characters).

ATTR%       The colour (or display attribute in monochrome modes) to
            be given to the text. This is calculated by the formula:

            Colour% = (Background% * 256) + Foreground%

            The GRATTRIB function (see below) will perform this
            calculation for you, automatically, using the foreground
            and background values you supply.

            Foreground and Background values are in the ranges used
            by the current video mode (eg. 0 - 15 for SCREEN 9). The
            actual colours displayed depend upon your current PALETTE
            settings.

            Note:   supplying a value of -1 for background prevents
                    background pixels from being changed at all. This
                    allows text to be blended more naturally into a
                    complex graphics display, it is not supported in
                    320 x 200 4-colour mode, however.

SCALE%      The character size of the text to be displayed. This ranges
            from 1 to 8, where 1 is standard 80-column text (40-column
            in SCREEN 7) and 8 multiplies the character size by eight
            on both the horizontal and vertical axes.

GRAPRINT can handle both byte-aligned and non byte-aligned characters. The
x, y co-ordinates you supply do not need to correspond to a row, column
character cell in SCREEN 0, the alphanumeric mode. The complete extended
ASCII character set is supported, including foreign symbols and box-
drawing characters (computers with CGA adaptors must have GRAFTBL loaded
to access characters above ASCII 127, however).

Since GRAPRINT does not support clipping, to ensure a clean display you
must ensure that the text to be output fits within the current screen
boundaries.

See also CGATEXT for displaying characters in SCREEN 1, MCGATEXT for
displaying characters in SCREEN 13 and VGATEXT for displaying text in
the EGA and VGA video modes (SCREENs 7-12).


HELPMATE

This routine provides a context-sensitive on-line Help facility for your
QuickBASIC programs.

DECLARE SUB HelpMate (BYVAL Colour%, Title$, BYVAL Context%, Topic$)

Colour%   is the display attribute to be given to the Help window. If a
          value of zero is passed, HELPMATE uses default colours which
          are Black on Cyan for colour screens and inverse video for a
          monochrome display.

Title$    is an optional Title for the Help window. If one is supplied
          it must be no longer than 48 characters so that it can be
          easily centered in the top row of the window. If Title$ is a
          null string, HELPMATE uses its' own name as a default.

Context%  is the context-sensitive flag. If set to 1, then the routine
          attempts to load the file specified by ...

Topic$    A legal DOS filename (up to 8 characters without extension),
          specifying the name of the Topic file to be displayed.
          HelpMate automatically appends the extension '.HLP'.

If Context% is not set, (or Topic$ is a null string), then the routine
displays a list of topics, from which you can make your own selection.

If Context% is set, HELPMATE will display the first page of the Topic file
specified, otherwise it begins by  overlaying the current screen with a
popup window in which is listed those HELP topics available.

The first topic in the list is highlighted and you can move the highlight
around the menu with the arrow keys Highlight the topic you want, then
press the <RETURN> key. The first page of that topic will be displayed in
the HELP window.

Page backwards and forwards through the file using the <PG UP> and <PG DN>
keys. If you page past the end of the file you will be returned to the
topic list, where you can either select another topic, or press <ESC> to
return to the QuickBASIC program. On return, the original screen and all
current variables are restored, intact, and program execution will
continue with the statement following the procedure call.

By default, the Toolbox Help system looks for its topic files in a sub-
directory called HELP, beneath the currently-logged directory. You can,
however, direct it to look elsewhere for files by setting a HELP variable
in the DOS environment table

e.g.  SET HELP=C:\BASIC\TOOLBOX\HELP

Alternatively, you can use the QuickBASIC ENVIRON statement within your
program, to point HELPMATE to the appropriate pathname. Remember, though,
that this method only remains in effect as long as the current program is
running and that there must be enough environment space available to hold
the HELP directory pathname.

A set of example Topic files, for use with the demonstration program,
DEMON.EXE is supplied with the Assembly-Language ToolBox. You can make
your own, using any Word Processor or Text Editor which can output plain
ASCII text (EDLIN will do). If you do so, bear in mind that the HelpMate
window's maximum page size is 16 rows of 55-column text. The maximum
number of pages in any one file is 256.

                             TIP

When displaying the list of available Topics, HelpMate searches the
current HELP directory for files with the extension .HLP. However, since
there is only room for 60 such filenames to be displayed in the menu
window, any files in excess of this number will be not be listed and are,
hence, inaccessible. You can, however, read any number of Context-
sensitive topic files since these are named explicitly in the call to
HelpMate which loads them. They need not, therefore, appear in the Topic
list.

If your application needs to provide a large number of Topic files, it is
a good idea to hide those which are context-sensitive from normal
directory searches (you can use the Toolbox Hide function to do this).
This will not prevent these files from being loaded when called, but it
does prevent them from appearing in the Topic list which gives you more
room for those general-purpose topic files which are selected by the user.

Note:       The \HELP directory on the ToolBox distribution disk
            contains a number of these hidden files for use by the
            demonstration program DEMON.EXE.


HIDE

Toggles the Hidden bit of the specified file's directory entry, making it
visible or invisible to directory listings.

DECLARE SUB Hide (BYVAL Switch%, FileSpec$)

If SWITCH% = 1 the file is hidden (regardless of whether it is currently
visible or not), any other value makes the file visible. FileSpec$ is the
name of the file to be hidden or unhidden. It can include a drive letter
and directory path but must be an explicit pathname, wildcard characters
are not allowed.


INTERVAL

Calculate the number of days between two dates supplied as long integer
Julian numbers. You can use the DAYNUMBER function (see above) to turn
dates in normal numeric format into Julian numbers and NUMBERDAY (below)
to convert them back again.

DECLARE FUNCTION Interval& (First&, Second&)

This function always returns a positive value, regardless of whether the
first argument is lower or greater than the second.


ITPRINT

Sends the text supplied, to the printer, as a string of italic characters.
Output begins at the current print position and can, optionally, append a
carriage-return/linefeed to take the print head to the beginning of a new
line when finished.

DECLARE SUB ItPrint (BYVAL Printer%, Buffer$, BYVAL NewLine%)

Arguments:  Printer%    the parallel port output is to be sent to
                        (1 = LPT1:, 2 = LPT2:, etc.).
            Buffer$     the string of text to be printed.
            NewLine%    set this to a non-zero value if you want
                        to move to a new line after printing.

The routine restores the previous print style or font before it returns
and does not effect subsequent output to the printer, using the QuickBASIC
LPRINT or PRINT # statements.

Note:       The version of this routine stored in the Toolbox
            library is for EPSON compatible printers. If you have
            an IBM graphics printer or ProPrinter, then you should
            rebuild your libraries, using either the PRINTIBM.OBJ
            or PRINTPRO.OBJ object module in place of PRINTEPS.OBJ.


KEYFLAGS

Returns a 16-bit unsigned number which is bit-encoded with the current
status of the CTRL, ALT, INSERT and other keyboard control keys.

No calling parameters are required.

DECLARE FUNCTION KeyFlags% ()

The BITTEST function (see below) can be used to isolate individual bits of
the returned value. Their meanings are as follows:

 F E D C B A 9 8 7 6 5 4 3 2 1 0   Bits
┌─┬─┬─┬─┬─┬─┬─┬─┬─┬─┬─┬─┬─┬─┬─┬─┐
│0│0│0│0│0│0│0│0│0│0│0│0│0│0│0│0│  Meaning if set
└─┴─┴─┴─┴─┴─┴─┴─┴─┴─┴─┴─┴─┴─┴─┴─┘
 │ │ │ │ │ │ │ │ │ │ │ │ │ │ └─┴─  Left & Right SHIFT keys pressed
 │ │ │ │ │ │ │ │ │ │ │ │ │ └─────  CTRL key pressed
 │ │ │ │ │ │ │ │ │ │ │ │ └───────  ALT key pressed
 │ │ │ │ │ │ │ │ │ │ │ └─────────  SCROLL LOCK active
 │ │ │ │ │ │ │ │ │ │ └───────────  NUM LOCK active
 │ │ │ │ │ │ │ │ │ └─────────────  CAPS LOCK active
 │ │ │ │ │ │ │ │ └───────────────  INSERT key status
 │ │ │ │ │ │ │ └─────────────────  Left CTRL key pressed
 │ │ │ │ │ │ └───────────────────  Left ALT key pressed
 │ │ │ │ │ └─────────────────────  SYS REQ key pressed
 │ │ │ │ └───────────────────────  PAUSE (or CTRL-NUM LOCK) active
 │ │ │ └─────────────────────────  SCROLL LOCK pressed
 │ │ └───────────────────────────  NUM LOCK pressed
 │ └─────────────────────────────  CAPS LOCK pressed
 └───────────────────────────────  INSERT key pressed

See the CAPSLOCK, NUMLOCK and SCRLOCK functions for a method of setting or
reading the status of specific control keys.


KEYFLUSH

This procedure flushes the keyboard type-ahead buffer and discards any
keystrokes which have not yet been processed.

No calling parameters are required.

DECLARE SUB KeyFlush ()

Note:       KEYFLUSH may not work properly if you have installed
            keystroke enhancement software which moves the type-ahead
            buffer to another location in memory. It DOES work with
            command-line buffers like IBM's DOSEDIT, however.


KEYIN

Similar to the QuickBASIC INKEY$ function, except that it waits for a
keypress instead of returning at once if none is available.

No calling parameters are required.

DECLARE FUNCTION KeyIn% ()

The function returns a numeric value between 0 and 255 which represents
the ASCII code of the key pressed. If one of the function keys (F1 to F12)
or a special key such as PAGEUP or one of the cursor arrows is pressed,
then a negative value is returned. Converting this number to its absolute
equivalent produces the scan code of the key.

Example:  KeyPress% = KeyIn%
          IF KeyPress% < 0 THEN
             ScanCode% = ABS(KeyPress%)
          ELSE
             AsciCode% = KeyPress%
          END IF

See the ASCICODE topic for a list of ASCII codes and their equivalent
printable characters. The SCANCODE topic lists the scan codes returned by
the various function and control keys.

The KEYIN function will recognise if one of the new 101/102 extended
keyboards is being used and return the correct scan codes for the extra
keys such as F11 and F12.


KEYSTAT

This function tests to see if a keystroke is waiting to be read. It does
not read or remove the keystroke from the typeahead buffer, use KEYIN% or
INKEY$ to do this.

No calling parameters are required.

DECLARE FUNCTION KeyStat% ()

KEYSTAT returns -1 (logical TRUE) if a keystroke is waiting to be
collected or 0 (logical FALSE) if the typeahead buffer is empty.


LPTSWAP

This procedure swaps the port addresses of the two printer channels
specified so that, for example, all output targeted to LPT1: will actually
be sent to LPT4:, and vice-versa.

DECLARE SUB LptSwap (BYVAL Printer1%, BYVAL Printer2%)

Printer1% and Printer2% are both numeric values in the range 1 - 4, where
1 = LPT1:, 2 = LPT2:, etc.

Note:       any changes made using LPTSWAP will remain in effect
            even after your program is finished.


MATHSCHIP

Checks to see if a floating-point maths co-processor is installed in the
system.

No calling parameters are required.

DECLARE FUNCTION MathsChip% ()

MATHSCHIP returns 0 (logical FALSE) if no co-processor is available. A
non-zero value indicates that a co-processor is available and, in this
case, the function will attempt to identify it. Possible return values
are:

     87 =   Intel 8087
    287 =   Intel 80287
    387 =   Intel 80387 (or 80486 with built-in maths processor)

Waitek and other models return the same values as their Intel equivalents.


MCGACOPY

Copies an MCGA screen to or from a user-supplied dynamic array.

DECLARE SUB McgaCopy (BYVAL Switch%, SEG Array)

SWITCH%     Direction of copy   0 = copy screen to string
                                1 = copy string to screen

ARRAY       Dynamic INTEGER or LONG integer array to hold the screen
            image. It must contain at least 64000 bytes of storage
            (32000 elements for INTEGER or 16000 for LONG) or the
            routine will fail, with possibly disastrous results.

Note:       It is not enough just to pass the name of the storage
            array to MCGACOPY. You must explicitly name the element
            where screen storage is to start, eg:

            DIM ScreenArray(1 TO 32000) AS INTEGER
            SCREEN 13
                .
            draw some stuff
                .
            McgaCopy 0, ScreenArray(1)


The QuickBASIC PCOPY statement is very useful for storing screen pages in
memory, so that they can be kept out of sight until needed. Unfortunately
it only works in text modes or, on computers with EGA or VGA video cards,
in SCREEN modes 7 to 12. This routine, on the other hand, works only in
the MCGA display mode (SCREEN 13), it provides a useful alternative to the
PCOPY statement for use with medium-resolution 256-colour screens.

See CGACOPY for a version that can be used with SCREEN 1 and 2 displays.


MCGASCROLL

Scrolls a rectangular portion of a SCREEN 13 (320 x 200 256-colour)
display one pixel to the left or right, wrapping those pixels which are
scrolled out at the end round to the beginning again.

DECLARE SUB McgaScroll (BYVAL xLoc%, BYVAL yLoc%, BYVAL xPixels%,_
                        BYVAL yPixels%, BYVAL Direction%)

XLOC%       The horizontal (X) co-ordinate of the top-left corner of
            the rectangle to be scrolled.

YLOC%       The vertical (Y) co-ordinate of the top-left corner of
            the rectangle to be scrolled.

XPIXELS%    The width (in pixels) of the rectangle to be scrolled.

YPIXELS%    The height (in pixels) of the rectangle to be scrolled.

DIRECTION%  The direction in which the rectangle contents are to be
            scrolled (0 = Left, 1 = Right).

Co-ordinates are in the ranges:  X >= 0 <= 319, Y >= 0 <= 199


MCGATEXT

Writes characters to the screen in the 320 x 200  256-colour graphics
mode (SCREEN 13).

DECLARE SUB McgaText (BYVAL xLoc%, BYVAL yLoc%, Text$,_
                      BYVAL Attr%, BYVAL Scale%)

This routine provides a convenient way of displaying text in SCREEN 13
without having to bother about loading external font files. It uses the
standard character definition tables built into your display adaptor, but
allows you to scale them up to eight times normal size and to specify any
combination of foreground and background colours.

XLOC%       The horizontal co-ordinate of the top left hand pixel
            from which the text will begin (0 - 319).

YLOC%       The vertical co-ordinate of the top left hand pixel
            from which the text will begin (0 - 199).

TEXT$       The string of text to be displayed (up to 63 characters).

ATTR%       The colour (or display attribute in monochrome modes) to
            be given to the text. This is calculated by the formula:

            Colour% = (Background% * 256) + Foreground%

            Foreground is in the range (0 - 255) and Background (0 - 64).
            The actual colours displayed depend upon your current PALETTE
            settings.

            Note:   supplying a value of -1 for background prevents
                    background pixels from being changed at all. This
                    allows text to be blended more naturally into a
                    complex graphics display.

SCALE%      The character size of the text to be displayed. This ranges
            from 1 to 8, where 1 is standard 40-column text and where 8
            multiplies the character size by eight on both the horizontal
            and vertical axes.

The complete extended ASCII character set is supported, including foreign
symbols and box-drawing characters.

Since MCGATEXT does not support clipping, to ensure a clean display you
must ensure that the text to be output fits within the current screen
boundaries.

See also CGATEXT for displaying characters in SCREEN 1 and VCGATEXT for
displaying characters in SCREENs 7-12.


MISTAKE

Displays the error message supplied in a dialogue box and waits for the
operator to press the <ENTER> key before returning, restoring the screen
to its' previous state.

DECLARE SUB MisTake (BYVAL Row%, Message$, BYVAL Attr%, BYVAL Mouse%)

ROW%        The top row of the dialogue box when it is displayed. The
            box is automatically centered within this row, which may be
            adjusted so that it remains within the screen boundaries.

MESSAGE$    A string of text comprising the error message to be displayed.
            It must be no longer than 40 characters otherwise it will be
            truncated to fit inside the display panel.

ATTR%       The display attribute or colour to be given to the dialogue box.
            If an argument of zero is supplied, the box is displayed with
            bright yellow text on a red background (colour monitors) or in
            reverse video (monochrome monitors).

MOUSE%     Should be set to TRUE (-1) or FALSE (0) to indicate if a
            mouse is available for use. If available, the operator can
            respond by clicking the left mouse button while the cursor is
            positioned on the radio button.

Note:       No meaningful value is returned by the procedure.


NETTEST

This function is used to detect if the program which calls it is running
under a Novell Network. It can be used to decide if file or record locking
is required.

No calling parameters are required.

DECLARE FUNCTION NetTest% ()

Returns -1 (logical TRUE) if the Network shell is present and 0 (logical
FALSE) if not. Note that the function cannot distinguish between programs
running on a local or network drive under NetWare.


NUMBERDAY

Splits a Julian date number into day, month and year and also returns the
day of the week as a number between 0 and 6 (0 = Sunday etc..)

DECLARE FUNCTION NumberDay% (Number&, Day%, Month%, Year%)


NUMLOCK

Toggles NUM LOCK on or off or, alternatively, reads the current NUM LOCK
key setting.

DECLARE FUNCTION NumLock% (BYVAL Switch%)

Switch% = 0  Turns NUM LOCK off
        = 1  Turns NUM LOCK on

Any other value just returns the current NUM status as a logical value
where -1 (TRUE) means that NUM LOCK is on and 0 (FALSE) means that NUM
LOCK is off.


PARALLELPORTS

This function checks how many hardware printer ports are available. It
does not check to see if an actual printer is connected to each of them,
use the PRINTEST or PRINTERSTAT functions (see below) to obtain this
information.

No calling parameters are required.

DECLARE FUNCTION ParallelPorts% ()


PAUSE

This routine is used to generate machine-independent timing loops. It
simply pauses until the specified number of clock ticks have elapsed.

DECLARE SUB Pause (BYVAL Ticks%)

There are 18.2 clock ticks per second on all PCs, no matter what the
processor or processor speed.


PEEKWORD

Reads a long integer value from two consecutive bytes of memory.

DECLARE FUNCTION PeekWord& (BYVAL Segment&, BYVAL Offset&)

Arguments:  Segment&  = address of memory segment containing the data
                        to be read.
            Offset&   = offset address, within the segment of the
                        two bytes to be read.

Returns:    contents of the two consecutive bytes in the form of a
            long integer value in the range (0 to 65535).

Note:       parameters are passed as LONG integers to save you the
            hassle of having to convert argument values over 32767
            to negative signed integers. Do not use values greater
            than 65535, however, or the most significant word will
            be ignored and the address converted to Modulus 65536.

            If you supply an offset address of 65535 (0FFFFh) which
            would cause the second byte to cross a segment boundary,
            only the lower byte is read and returned as a value
            between (0 - 255).

Using QuickBASIC's PEEK function to examine data which lies outside
of DGROUP is a pain. You also have to use DEF SEG to set the segment
required and then to reset it afterwards. This function allows you to
read data, directly, from anywhere in the 1 megabyte of addressable
RAM space your computer contains. It also reads two adjacent bytes of
data from the address supplied and converts them to a single integer.

The PC architecture follows the Intel convention of storing 'words'
(two-byte values) with the Least Significant part in the lower byte
(LSB) and the Most Significant (MSB) in the higher byte. Since each
byte can only hold 256 possible values (0 to 255), an integer which
has a range of from 0 to 65535 (unsigned) is stored in consecutive
bytes with the MSB being considered the number of times it can be
divided by 256 and the LSB being the remainder of this division. The
number 1000, for example would be stored in memory as follows:

                         LSB              MSB
                 ┌─┬─┬─┬─┬─┬─┬─┬─┐ ┌─┬─┬─┬─┬─┬─┬─┬─┐
1000 (decimal) = │1│1│1│0│1│0│0│0│ │0│0│0│0│0│0│1│1│
                 └─┴─┴─┴─┴─┴─┴─┴─┘ └─┴─┴─┴─┴─┴─┴─┴─┘

                 1000 MOD 256 = 232   1000 \ 256 = 3

To convert the two bytes back to a single integer again, you would
use the formula:

                        x = (MSB * 256) + LSB

or, in our example:     x = 3 * 256 + 232 = 1000

PEEKWORD makes this conversion for you automatically, all you have to
do is supply the address and it returns the contents of the two bytes
in long integer format.

The POKEWORD procedure (below) complements PEEKWORD by allowing you
to write a word of data anywhere in the 1MB addressable PC workspace.

See also FARPEEK and FARPOKE which allow you to read from and write
to far memory, one byte at a time.


POKEWORD

Writes an integer value into two consecutive bytes of memory.

DECLARE SUB PokeWord (BYVAL Segment&, BYVAL Offset&, BYVAL Word&)

Arguments:  Segment&  = address of memory segment containing the
                        location to be written to
            Offset&   = offset address, within the segment of the
                        two bytes to be set.
            Word&     = the value to set in memory. It must be a
                        value in the range 0 to 65535.

The data is written in standard Intel format, with the Most
Significant part of the number (MSB) being written into the higher
of the two bytes.

Note:       if you supply an offset address of 65535 (0FFFFh) which
            would cause the second byte to cross a segment boundary,
            only the lower, least significant, byte (LSB) is written.

            Parameters are passed as LONG integers to save you the
            hassle of having to convert argument values over 32767
            to negative signed integers. Do not use values greater
            than 65535, however, or the most significant word will
            be ignored and the address converted to Modulus 65536.

The PEEKWORD procedure (above) complements POKEWORD by allowing you
to read a word of data from anywhere in the 1MB of addressable PC
memory.

See also FARPEEK and FARPOKE which allow you to read from and write
to far memory, one byte at a time.


POPUP

This is the Toolbox popup window generator. What are Windows?  Well if
you've used the QuickBASIC environment at all then you've used Windows.
When you press <ALT><F> to bring down the File Menu, the list of options
presented there is in a window. Notice how any characters which were
concealed when the File Menu appeared, are restored, intact, after you've
made your choice. Windows are areas of the screen which are used to hold
transient data and messages to the user. They make the most of the limited
display space available and remove the need to constantly rebuild the
screen, each time your program communicates with the world.

Properly  presented, windows can give the illusion of multi-tasking, even
on single-processor machines like the IBM-PC.

Nowadays, no program worth its' salt can be without a window of some kind.
If YOUR program is going to stand out amongst all the others, however,
they've got to be done professionally. Windows must appear instantly and
vanish, just as quickly, when no longer required. They must be as large or
as small as is necessary, for the data which you need to display, and you
should have a plentiful supply, for all the circumstances that your
program might encounter. BASIC, unfortunately, is just not fast enough to
meet all these requirements.

Looks like it'll have to be Assembly-Language again ...

DECLARE SUB PopUp (BYVAL Row%, BYVAL Col%, BYVAL Hght%, BYVAL Wdth%,_
                   BYVAL Attr%, BYVAL Brdr%, BYVAL Shdw%, BYVAL Zoom%)

Opens a popup window at the screen location specified.

Where:    P1%  is the top-left row co-ordinate
          P2%  is the top-left column co-ordinate
          P3%  is the height (in rows) of the window
          P4%  is the width (in columns) of the window
          P5%  is the display attribute or colour
          P6%  is the border style (0 = no border)
          P7%  is the shadow switch (0 = no shadow)
          P8%  is the zoom switch (0 = no zoom)

The first four parameters specify the size of the window and the location
on the screen at which it will appear. Border styles are as follows:

┌────┐
│ 1. │    Single-lined box all round the window
└────┘
╔════╗
║ 2. ║    Double-lined box all round the window
╚════╝
╒════╕
│ 3. │    Single vertical, double horizontal
╘════╛
╓────╖
║ 4. ║    Single horizontal, double vertical
╙────╜
╤════╤
│ 5. │    Single-lined box all round the window
╘════╛
╦════╦
║ 6. ║    Double-lined box all round the window
╚════╝
┬────┬
│ 7. │    Single vertical, double horizontal
╘════╛
╥────╥
║ 8. ║    Single horizontal, double vertical
╙────╜

Border styles 5 through 8 are particularly suitable for use with pull-
down menus, descending from a horizontal bar.

The SHADOW switch (Parameter 7), can be used to add a black shadow beneath
your window, Giving it a three dimensional effect. Setting P7% to 1 puts
solid shadow on the left-hand side. Setting P7% to 2 puts it on the right.
values of 3 and 4 in P7% will display transparant shadow to the left or
right, respectively, any other value prevents shadow.

Setting Parameter 8 to a non-zero value will cause the window to ZOOM onto
the screen.  What this means is that, starting at a point source,
successively larger versions of the window will be drawn until it is the
size required. The value you supply sets the interval, in milliseconds,
between iterations and is used to control the speed at which the window
explodes onto the screen.

To preserve compatibility with programs written for use with previous
versions of the Toolbox, a value of 1 in parameter 8 sets the default
delay of 20 milliseconds per iteration. At this speed, which is constant
on PCs with all types of microprocessor, the process is extremely fast
and impressive, and adds a very professional touch to your programs.

Before a window is opened, the display area below it is copied to an
internal buffer, from where it will be eventually restored when the window
is closed. This buffer has a capacity of 8 KiloBytes, the equivalent of
two full screens. To calculate the storage required for a particular
window, use the formula:

Bytes = ((Height in rows * Width in columns) * 2) + 6

(add one row to the height and one column to the width if you specify
shadow)

The window area needs to be multiplied by 2 since each screen character
takes two bytes of memory, for itself and its attribute code. The odd six
bytes are required for the storage of buffer pointers. The window buffer
works as a LIFO (Last In First Out) stack, so that the last window opened
is the first one to be removed. You can close the current window with the
statement:

CALL ShutUp

To put text inside a window, use the FASTPRINT routine (see above). You
can clear all or part of an open window with SCROLL (see below).


PRINTERSTAT

DECLARE FUNCTION PrinterStat% (BYVAL Printer%)

This function tests the current status of the parallel printer specified.
The value returned is tested as follows :

   Bit     Wanted    Meaning
─────────────────────────────────────────────────────
    7        1       Printer not busy (0 = busy)
    6        0       Printer acknowledges
    5        0       Out-of-paper
    4        1       This printer selected
    3        0       I/O error
    2        0       Not used
    1        0       Not used
    0        0       Time-out occurred
─────────────────────────────────────────────────────
   90 Hex  144 (Decimal)

Specify the printer to be tested as a number between 1 and 4, where 1 =
LPT1:, 2 = LPT2:, etc.

Note:       Some printers also set the acknowledgement bit. If so, the
            value returned will be 208 (D0 Hex) instead of 144.


PRINTEST

This is a simplified version of the PRINTERSTAT function (above). It
returns a logical value to indicate whether the specified printer is ready
(TRUE = -1) or not (FALSE = 0).

DECLARE FUNCTION PrinTest% (BYVAL Printer%)

Specify the printer to be tested as a number between 1 and 4, where 1 =
LPT1:, 2 = LPT2:, etc. The function will only work with parallel printers.


PRINTSET

Most modern printers have a variety of useful styles and fonts which you
can select by setting dip switches or sending the appropriate control
codes from the computer. Unfortunately this is not always convenient,
especially when you are in the middle of a program and have to duck out to
set up the proper print size. PRINTSET offers a solution to this problem
in the form of a pull-down menu which allows you to select from a range of
printer features, using the 'point-and-shoot' method.

DECLARE SUB PrintSet (BYVAL Row%, BYVAL Col%, BYVAL Attr%, BYVAL Printer%)

Where:  Row%     = Row number of the top left-hand corner of the menu
                   window.
        Col%     = Column number of the top left-hand corner of the menu
                   window.
        Attr%    = the display attribute or colour which is given to the
                   menu window.
        Printer% = the printer number (i.e. 1 = LPT1, 2 = LPT2 etc).

If you supply a value of zero for the Attr% argument, the menu window will
take the colour or attribute of the character which will be overlaid by
the top left corner of the window, when it appears. If this character is
also a single or double-lined horizontal bar (ASCII 196 or 205), the
border of the menu will be automatically adjusted to blend in with this
line, allowing you to produce the appearance of a pulldown menu.

Note:       Although the Toolbox package contains copies of this module
            configured for different types of printer, only one version
            of PrintSet may be in the library at any one time.

            PRINTEPS.OBJ is for Epson printers
            PRINTIBM.OBJ is for IBM Grahics printers
            PRINTPRO.OBJ is for IBM Proprinters


RAMDISK

Many disk-intensive processes, such as file sorting, will run much faster
when performed on a ramdisk. In such cases, use this function to test if a
ramdisk is available and the FREESPACE function (above) to see if it has
enough space for the job required. Don't forget to copy your data back to
a physical drive afterwards, or you will lose it when you power off.

RAMDISK searches the system drive table and examines the device driver for
each block device to see if it is a ramdisk. If one is detected, the
function returns the ASCII value of the drive letter associated with it
(eg 68 = D:). If no ramdisk is present, a value of zero is returned. If
more than one ramdisk is present in the system, only the first one is
reported on.

No calling parameters are required.

DECLARE FUNCTION RamDisk% ()

RAMDISK will work reliably with all versions of Microsoft's RAMDRIVE and
IBM's VDISK. However it has not been tested with any of the more esoteric
virtual disk products, and may not correctly identify some of these.


RAND

Returns a random number. This differs from QuickBASIC's RND function in
that RAND returns an integer and you can specify the range for this value.

DECLARE FUNCTION Rand% (BYVAL Lower%, BYVAL Higher%)

Lower% and Higher% are the upper and lower limits for the random number
to be returned. If Lower% is greater than Higher% then the arguments will
be transposed.


RESEED

Reinitialises the random number seed used by the RAND function (above).

DECLARE SUB ReSeed (BYVAL Seed&)

Note that the argument passed is a LONG integer. This enables you to use
the value which is returned by the QuickBASIC TIMER function, eg:

    ReSeed TIMER

Note that the Toolbox random number seed is not the same as the one used
internally by QuickBASIC. You cannot, therefore, start a new sequence of
QB's RND values by using RESEED nor can you use RANDOMIZE to reinitialise
the sequence for RAND.

SCREENDUMP

Copies the contents of the current screen (text mode only) to the line
printer, just as if the operator had pressed the <Prt Scrn> key.

No calling parameters are required.

DECLARE SUB ScreenDump ()

Includes support for 43 and 50-line screens on EGA and VGA adaptors.

This routine will not work if screen print has previously been disabled by
a call to the DISABLEPRTSC routine (see above) or if the parallel printer
at LPT1: is not ready.


SCREENROWS

Returns the height of the current screen, in rows, as set by the last
WIDTH statement (default = 25).

No calling parameters are required.

DECLARE FUNCTION ScreenRows% ()

The number returned may be 25, 43 or 50, depending on the capabilities of
your display adaptor.


SCREENWIDTH

Returns the width of the current screen, in columns, as set by the last
WIDTH statement.

No calling parameters are required.

DECLARE FUNCTION ScreenWidth% ()

Possible return values are 40 and 80 (default = 80).


SCRLOCK

Toggles SCROLL LOCK on or off or, alternatively, reads the current SCROLL
LOCK key setting.

DECLARE FUNCTION ScrLock% (BYVAL Switch%)

Switch% = 0  Turns SCROLL LOCK off
        = 1  Turns SCROLL LOCK on

Any other value just returns the current SCROLL status as a logical value
where -1 (TRUE) means that SCROLL LOCK is on and 0 (FALSE) means that the
SCROLL LOCK is off.


SCROLL

Scrolls the contents of a screen rectangle a specified number of lines or
columns in the direction indicated, blank spaces of the background colour
specified are scrolled in to replace them.

DECLARE SUB Scroll (BYVAL Dir%, BYVAL Y1%, BYVAL X1%, BYVAL Y2%,_
                    BYVAL X2%, BYVAL Units%, BYVAL Attr%)

Dir%        =  Scroll direction (0 = down, 1 = up, 2 = left, 3 = right).
Y1%         =  Top-left row of rectangle to be scrolled.
X1%         =  Top-left column of rectangle.
Y2%         =  Bottom-right row of rectangle.
X2%         =  Bottom-right column of rectangle
Units%      =  Number of rows or columns to scroll.
Attr%       =  Display attribute of blank spaces scrolled in.

Notes:      This routine will work in all graphics modes as well as on
            the text screen. When scrolling the graphics screen up or
            down, however, the attribute value must be calculated in a
            different way:

            On 320 x 200 4-colour and 640 x 200 2-colour displays the
            attribute represents a 1-byte pixel pattern, which is
            equivalent to 8 pixels in 2-colour (SCREEN 2) mode and 4
            pixels in 4-colour (SCREEN 1) mode. This pixel pattern is
            replicated through all the blank lines scrolled in.

            In all other EGA, VGA and MCGA display modes, ATTR% is
            the colour value for each pixel in the blanked lines.

            Scrolling sideways in graphics modes, using this routine,
            does not provide sufficiently fine movement for animation
            effects, but see the CGASCROLL and MCGASCROLL procedures
            (above) for a more precise alternative.


SECURE

Toggles bit zero of the specified file's directory entry, making it either
Read-only or Read/Write.

DECLARE SUB Secure (BYVAL Switch%, FileSpec$)

If SWITCH% = 1 the file is made Read-only (regardless of whether it can be
currently written to or not), any other value makes the file Read/Write.
FILESPEC is the name of the file to be hidden or unhidden. It can include
a drive letter and directory path but must be an explicit pathname,
wildcard characters are not allowed.


SERIALPORTS

This function checks how many serial ports are available, it does not
check to see if devices are connected to any of them.

No calling parameters are required.

DECLARE FUNCTION SerialPorts% ()


SHARE

Toggles bit seven of the specified file's directory entry, making it
either Shareable or Non-shareable. This routine will only work when the
program which calls it is running under a Novell Network.

DECLARE SUB Share (BYVAL Switch%, FileSpec$)

If SWITCH% = 1 the file is made Shareable (regardless of whether it can be
currently used by other programs or not), any other value makes the file
Non-shareable. FILESPEC is the name of the file to be shared. It can
include a drive letter and directory path but must be an explicit
pathname, wildcard characters are not allowed.


SHUTUP

Closes the last window opened by the POPUP window procedure (see above)
and restores the contents of the screen below it.

DECLARE SUB ShutUp (BYVAL Speed%)

The Speed% parameter is a delay in milliseconds. If greater than zero
it produces the effect of imploding the storage buffer contents onto the
screen, making the window appear to vanish into a point source.


SIZEOF

This function will return the size of the file specified in bytes, or, if
more than one match is found, the total size of all such files. If a size
of zero is returned, no matching file exists (at least not in the
directory specified).

DECLARE FUNCTION SizeOf& (FileSpec$)

The filename can include a directory path and may be ambiguous, using the
wildcard characters '*' and '?'.


SOUNDEX

Gets the phonetic equivalent of a string. This function returns a long
integer which represents the 'sound' of a string of text using the SOUNDEX
phonetic conversion algorithm. It can be used in 'fuzzy' searches, for
example, to scan a database for an individual when you are not sure of the
exact spelling of their surname. When searching for SMITH, for instance,
SOUNDEX would also match SMYTH and SMYTHE.

DECLARE FUNCTION Soundex& (Text$)

Note that the initial letter of the search string must exactly match the
initial letter of the target. GAMMELL and CAMMEL will return different
values when passed to SOUNDEX. Note also that the function will only
convert the first word of the string, translation stops at the first
blank space.


SPOOLER

Gets the installed state of the DOS print spooler, PRINT.COM, so that a
program can check if it is safe to submit files to the print queue.

No calling parameters are required.

DECLARE FUNCTION Spooler% ()

Returns:    -1  if spooler is installed
             0  if spooler is not installed


SPOOLDELETE

Deletes one or more files from the current print queue.

FileSpec$ should include the full pathname of the file to be deleted from
the print queue. It can be ambiguous, using the DOS wildcard characters
'*' and '?', allowing you to cancel the processing of a range of files
with a single command.

DECLARE SUB SpoolDelete (FileSpec$)

Note:       This function will only work if PRINT.COM, the DOS print
            spooler has been installed. You can use the SPOOLER
            function (see above) to check if PRINT.COM is available.


SPOOLFLUSH

Deletes all files from the current print queue and terminates output to
the printer.

No calling parameters are required.

DECLARE SUB SpoolFlush ()

Note:       This function will only work if PRINT.COM, the DOS print
            spooler has been installed. You can use the SPOOLER
            function (see above) to check if PRINT.COM is available.


SPOOLLIST

Returns the pathname of a file in the current print queue.

SPOOLLIST can only be used while printing is suspended after a call to the
SPOOLSUSPEND function (see below) has been made.

Buffer$ must be preset to a length of at least 64 bytes for the routine to
work, although you do not have to fill it with spaces first.  When called,
immediately after printing has been suspended, SPOOLLIST will return, in
Buffer$, the pathname of the first file in the spooler print queue.

Further calls will return the names of subsequent files in the queue until
a string of blank spaces indicates that all entries have been read.

DECLARE SUB SpoolList (Buffer$)

The following example demonstrates how SPOOLLIST, SPOOLSUSPEND and
SPOOLRESTART can be used in a QuickBASIC program.

    CONST FALSE = 0, TRUE = NOT FALSE

    Buffer$ = STRING$(64, "*")

    Status% = SpoolSuspend%
    PRINT "Spooler suspended, status is"; Status%
    PRINT "Files in print queue are ...": PRINT
    Done% = FALSE: Number% = 1
    DO
        SpoolList Buffer$
        IF Buffer$ = SPACE$(64) THEN
           Done% = TRUE
        ELSE
           PRINT Number%, Buffer$
           Number% = Number% + 1
       END IF
    LOOP UNTIL Done%
    CALL SpoolReStart
END

Use SPOOLRESTART (see below) to resume printing after it has been
suspended for a listing of the queue contents to be made.

Note:       This function will only work if PRINT.COM, the DOS print
            spooler has been installed. You can use the SPOOLER
            function (see above) to check if PRINT.COM is available.


SPOOLRESTART

Re-enables output of spooled files to the printer after it has been
suspended for a status check or for the queue contents to be listed.

No calling parameters are required.

DECLARE SUB SpoolReStart ()

Note:       This function will only work if PRINT.COM, the DOS print
            spooler has been installed. You can use the SPOOLER
            function (see above) to check if PRINT.COM is available.


SPOOLSUBMIT

Submits a file for processing by the DOS print spooler.

FileSpec$ should contain the full pathname of the file to be printed and
should be no longer than 64 characters. Wildcard characters are not
allowed. If found, the file will be added to the end of the current print
queue.

DECLARE SUB SpoolSubmit (FileSpec$)

Note:       This function will only work if PRINT.COM, the DOS print
            spooler has been installed. You can use the SPOOLER
            function (see above) to check if PRINT.COM is available.


SPOOLSUSPEND

Suspends output from the DOS print spooler and reports if an error has
been encountered. Printing is suspended until you use the SPOOLRESTART
procedure (see above) to resume output.

No calling parameters are required.

DECLARE FUNCTION SpoolSuspend% ()

Returns:     0 = no errors
             1 = invalid function
             2 = file not found
             3 = path not found
             4 = too many open files
             5 = access denied
             8 = queue full
             9 = spooler busy
            12 = name too long
            15 = invalid drive

SPOOLLIST (see above), which returns the pathnames of files in the print
queue, can only be called while the spooler is suspended.

Note:       This function will only work if PRINT.COM, the DOS print
            spooler has been installed. You can use the SPOOLER
            function (see above) to check if PRINT.COM is available.


STATUSLINE

This procedure displays the message supplied on the bottom line of the
display, prompts the user for a keypress, waits until it is received and
then returns, restoring the screen to its former state. The  ASCII value
of the keypress is returned in the variable that you assign to the
function.

DECLARE FUNCTION StatusLine% (Message$)

Note:       StatusLine will recognise if an EGA or VGA is installed and
            will correctly locate itself if the screen is in 43 or 50-
            line mode.


STRINGSCAN

This routine searches a variable-length string array for the string
specified, returning the element number it occupies if found.

DECLARE FUNCTION StringScan% (Trgt$, BYVAL Size%, BYVAL Strt%, BYVAL Addr%)

Arguments:  Trgt$ = target string to be searched for.
            Size% = number of array elements to be searched.
            Strt% = array element to start searching at.
            Addr% = address of start element (the VARPTR value).

See also the STRINGSORT routine (below) for a fast method of sorting a
variable-length string array.


STRINGSORT

This procedure can sort a string array into ascending or descending order,
very quickly indeed.

DECLARE SUB StringSort (BYVAL Dir%, BYVAL Size%, BYVAL Addr%)

Arguments:  Dir%    = sort direction (0 = ascending, 1 = descending).
            Size%   = number of elements to sort.
            Addr%   = VARPTR of element to start sorting from.

Note:       This routine now works perfectly with Extended QuickBASIC
            far string arrays, provided that the range of elements to
            sort are contained within a single 64K segment. If the
            array extends over more than one segment then no sorting
            will be performed at all.


ULPRINT

Sends the text supplied, to the printer, as a string of underlined
characters.  Output begins at the current print position and can,
optionally, append a carriage-return/linefeed to take the print head to
the beginning of a new line when finished.

DECLARE SUB UlPrint (BYVAL Printer%, Buffer$, BYVAL NewLine%)

Arguments:  Printer%    the parallel port output is to be sent to
                        (1 = LPT1:, 2 = LPT2:, etc.).
            Buffer$     the string of text to be printed.
            NewLine%    set this to a non-zero value if you want
                        to move to a new line after printing.

The routine restores the previous print style or font before it returns
and does not effect subsequent output to the printer, using the QuickBASIC
LPRINT or PRINT # statements.

Note:       The version of this routine stored in the Toolbox
            library is for EPSON compatible printers. If you have
            an IBM graphics printer or ProPrinter, then you should
            rebuild your libraries, using either the PRINTIBM.OBJ
            or PRINTPRO.OBJ object module in place of PRINTEPS.OBJ.


VERIFY

This function opens a dialogue box, centered at the screen row specified,
in which is displayed a prompt supplied by the caller. The routine adds a
further Y/N prompt, and then waits for a keypress. Only <Y/N> responses
(in upper or lower case) are accepted and the value that is returned
evaluates to Boolean TRUE (-1), if a Y(es) response was entered, and
Boolean FALSE (0) if the reply was N(o). The screen is restored to its
previous state on exit from the function.

DECLARE FUNCTION Verify% (BYVAL Default%, BYVAL Row%, Prompt$,_
                          BYVAL Attr%, BYVAL Mouse%)

DEFAULT%    Specifies the radio button to be highlighted as the default
            response on entry into the function. Pressing <Return> or
            clicking the left mouse button without moving the pointer
            will produce the specified response. If DEFAULT% is set to
            one the YES button is highlighted. Any other value highlights
            the NO button.

ROW%        The top row of the dialogue box when it is displayed. The
            box is automatically centered within this row, which may be
            adjusted so that it remains within the screen boundaries.

PROMPT$     A string of text comprising the message to be displayed. It
            must be no longer than 40 characters otherwise it will be
            truncated to fit inside the display panel.

ATTR%       The display attribute or colour to be given to the dialogue box.
            If an argument of zero is supplied, the box is displayed with
            bright white text on a blue background (colour monitors) or in
            reverse video (monochrome monitors).

MOUSE%      should be set to TRUE (-1) or FALSE (0) to indicate if a mouse
            is installed and can be used to respond.

Notes:      The user can respond, either by pressing the <Y> or <N> keys
            or by using <TAB> to highlight the appropriate radio button
            and then pressing <RETURN>.

Mouse support has now been added, enabling the operator to respond by
clicking the mouse cursor on the appropriate radio button.


VGADIM

Allows a program running on a computer fitted with VGA to dim or brighten
the display intensity.

DECLARE SUB VGADim (BYVAL Intensity%)

Intensity% is a number in the range -63 to +63 which sets the brightness
of the screen relative to the default value (zero).


VGALOAD

Loads EGA, VGA and MCGA screens into video memory from disk. This is an
alternative to the QuickBASIC BLOAD statement which cannot be used with
the higher-resolution graphics displays provided by SCREEN modes 7 to 13.

DECLARE SUB VGALoad (File$)

FILE$ must be a legal DOS filename, including extension, drive letter and
directory path where appropriate.

Note:       The screen image must have been previously written to a disk
            file using the VGASAVE procedure (see below) and should have
            the same resolution as that provided by the current SCREEN.


VGAPAN

Sets the display window co-ordinates for EGA, VGA and MCGA screens.

This procedure sets the origins of display window within the video display
buffer used by the EGA, VGA and MCGA adaptors.  Normally this is at the
top left-hand corner of the graphics image, but by changing co-ordinates
you can pan the display through video memory, to create some interesting
animation effects.

DECLARE SUB VGAPan (BYVAL X%, BYVAL Y%)

Example program

' OUTPAN.BAS - pans the virtual screen window on EGA and VGA
'              display adaptors.
'
'   Author:    Christy Gemmell
'   For:       Assembly-Language ToolBox for QuickBASIC
'   Date:      11/12/89
'
    DECLARE FUNCTION KeyIn% ()
    DECLARE SUB VGAPan (BYVAL X%, BYVAL Y%)

    CONST FALSE = 0, TRUE = NOT FALSE

    SCREEN 9: LINE (0, 0)-(639, 349), 9, BF
    VIEW SCREEN (40, 25)-(600, 325), 0, 15
    CIRCLE (319, 174), 150, 14: PAINT (319, 174), 14, 14

    X% = 0: Y% = 0

    DO
        KeyPress% = KeyIn%: Pan% = TRUE
        SELECT CASE KeyPress%
            CASE -75
                IF X% > 0 THEN X% = X% - 1
            CASE -77
                IF X% < 79 THEN X% = X% + 1
            CASE -72
                IF Y% > 0 THEN Y% = Y% - 1
            CASE -80
                IF Y% < 22 THEN Y% = Y% + 1
            CASE ELSE
                Pan% = FALSE
        END SELECT
        IF Pan% THEN VGAPan X%, Y% * 5
    LOOP UNTIL KeyPress% = 27
END


VGASAVE

Saves EGA, VGA and MCGA screens from video memory to disk.

The normal QuickBASIC BLOAD and BSAVE statements only work properly with
text and CGA graphics screens. This routine allows you to do the same
with higher-resolution graphic displays in SCREEN modes 7 to 13.

DECLARE SUB VGASave (File$)

FILE$ must be a legal DOS filename, including the extension, drive letter
and directory path where appropriate.

A companion procedure, VGALOAD (see above) is provided to allow you to
retrieve the graphics image from disk, and restore it to the screen.

Example program

' VGAFILE.BAS  saves and loads a high-resolution graphics image
'
'   Author:     Christy Gemmell
'   For:        Assembly-Language ToolBox for QuickBASIC
'   Date:       11/12/89
'
'   Graphics converted from Microsoft Extended Color BASIC
'
    DECLARE SUB VGALoad (File$)
    DECLARE SUB VGASave (File$)

    ScreenMode% = 12              ' Try other modes as well

    SELECT CASE ScreenMode%
        CASE 7, 13
             xMax% = 319: yMax% = 199
        CASE 8
             xMax% = 639: yMax% = 199
        CASE 9, 10
             xMax% = 639: yMax% = 349
        CASE 11, 12
             xMax% = 639: yMax% = 479
        CASE ELSE
    END SELECT

    SCREEN ScreenMode%: KEY OFF
    LINE (0, 0)-(xMax%, yMax%), 6, BF
    VIEW (32, 4)-(xMax% - 32, yMax% - 4), 0, 5
    WINDOW SCREEN (0, 0)-(255, 191)
    FOR I% = 1 TO 40
        READ A%, B%, C%, D%: LINE (A%, B%)-(C%, D%), 1
    NEXT I%
    PAINT (56, 20), 1, 1: PAINT (136, 64), 1, 1
    PAINT (120, 80), 1, 1: PAINT (192, 88), 14, 1
    PAINT (76, 48), 14, 1: PAINT (124, 60), 14, 1
    PAINT (68, 12), 2, 1: PAINT (80, 84), 2, 1
    PAINT (92, 128), 2, 1: PAINT (36, 156), 12, 1
    PAINT (36, 168), 1, 1: PAINT (84, 178), 14, 1
    PAINT (88, 118), 12, 1: PAINT (144, 86), 12, 1
    VGASave "ESCHER.IMG": SLEEP 1: CLS : SLEEP 3
    VGALoad "ESCHER.IMG": R$ = INPUT$(1)
END

DATA    68,4,200,76,52,12,112,44,128,52,172,76,128,52,68,84,112,44,84,60
DATA    128,68,99,84,68,36,97,52,128,68,154,84,128,68,128,116,128,52,128
DATA    68,68,4,52,12,172,76,142,90,142,76,142,108,142,108,200,76,200,76
DATA    200,92,200,92,68,164,128,116,84,140,52,12,52,154,52,154,68,164
DATA    68,164,68,100,68,36,68,84,84,45,84,76,84,109,84,140,68,100,97,116
DATA    84,124,112,108,68,84,128,116,84,76,112,92,112,77,112,108,84,119
DATA    92,114,142,86,151,82,180,66,186,62,186,62,236,90,236,90,68,184
DATA    68,184,16,154,16,154,52,133,16,154,16,160,16,160,68,190,68,190
DATA    68,184,68,190,236,96,236,96,236,90


VGATEXT

Writes characters to the screen in EGA and VGA graphics modes.

DECLARE SUB VgaText (BYVAL xLoc%, BYVAL yLoc%, Text$,_
                     BYVAL Attr%, BYVAL Scale%)

This routine provides a convenient way of displaying text in any of the
EGA and VGA graphics modes (SCREENs 7-12) without having to bother about
loading external font files. It uses the standard character definition
tables built into your display adaptor, but allows you to scale them up to
eight times normal size and to specify any combination of foreground and
background colours supported by the current video mode.

XLOC%       The horizontal co-ordinate of the top left hand pixel
            from which the text will begin

YLOC%       The vertical co-ordinate of the top left hand pixel
            from which the text will begin

TEXT$       The string of text to be displayed (up to 63 characters).

ATTR%       The colour (or display attribute in monochrome modes) to
            be given to the text. This is calculated by the formula:

            Colour% = (Background% * 256) + Foreground%

            Foreground and Background values are in the ranges used
            by the current video mode (eg. 0 - 15 for SCREEN 9). The
            actual colours displayed depend upon your current PALETTE
            settings.

            Note:   supplying a value of -1 for background prevents
                    background pixels from being changed at all. This
                    allows text to be blended more naturally into a
                    complex graphics display.

SCALE%      The character size of the text to be displayed. This ranges
            from 1 to 8, where 1 is standard 80-column text (40-column
            in SCREEN 7) and 8 multiplies the character size by eight
            on both the horizontal and vertical axes.

VGATEXT can handle both byte-aligned and non byte-aligned characters. The
x, y co-ordinates you supply do not need to correspond to a row, column
character cell in SCREEN 0, the alphanumeric mode. The complete extended
ASCII character set is supported, including foreign symbols and
box-drawing characters.

Since VGATEXT does not support clipping, to ensure a clean display you
must ensure that the text to be output fits within the current screen
boundaries.

See also CGATEXT for displaying characters in SCREEN 1 and MCGATEXT for
displaying characters in SCREEN 13.


WEEKDAY

This function is used to determine the day of the week for a given date.
It does this by temporarily resetting the system date to the one supplied,
reading the day from DOS, and then restoring the old date. The weekday is
returned as a number between 0 and 6, signifying Sunday through Saturday.

DECLARE FUNCTION WeekDay% (BYVAL Day%, BYVAL Month%, BYVAL Year%)


──────────────────────────────────────────────────────────────────────

EXTRA ROUTINES FOR QB4

The following functions and procedures are only included in the version of
the Toolbox intended for QuickBASIC 4.x and BASIC 6. They are omitted from
the later version because the Extended QuickBASIC language provided with
the BASIC 7 Professional Development System includes new statements and
functions that render them unneccessary. Well they say that imitation IS
the sincerest form of flattery!


FINDFIRST

This routine sets the Disk Transfer Address to point to a local buffer and
then attempts to find a match for the file specified in WildCard$. If one
or more matches are found, the filename of the first matching file (minus
directory path), is stuffed into the second string argument. If no match
is found, this string is filled with blank spaces.

DECLARE SUB FindFirst (Attr%, WildCard$, Match$)

WildCard$ can contain an ambiguous filename, using the wildcard characters
* and ?, in which case FINDFIRST will only find the first matching file.
To obtain the names of any subsequent matches, use the FINDNEXT function
(see below).

Match$ must be at least twelve characters long to hold the returning
filename and extension. You do not need to clear the string first as the
function does that for you, automatically.

Normally, only visible files with full read\write access are found, but
you can extend this to search for hidden, read-only or system files as
well by setting the Attr% parameter to the appropriate attribute value.

   Attr% = 0   Visible read\write
           1   Read-only files
           2   Hidden files
           4   System files

Do not use the SIZEOF function while searching for files with FINDFIRST
and FINDNEXT. Since both routines relocate the DOS Disk Transfer Address
during operation, this may lead to a conflict which will cause your
program to lose track of one or more open files. You should, in any case,
always use the RESETDTA routine to restore the Disk Transfer Address after
FINDFIRST/FINDNEXT is completed.

The DIR$ function which Microsoft have added to Extended QuickBASIC (QBX)
provides a built-in FINDFIRST/FINDNEXT service which makes the Toolbox
routines redundant. They are, therefore, omitted from the BASIC 7 version.


FINDNEXT

Finds successive matches of an ambiguous filename after a previously
successful call to FINDFIRST (see above). You can call it repeatedly
until a blank string is returned in Match$, in which case there are
no more files to be found.

DECLARE SUB FindNext (Match$)

Match$ must be at least twelve characters long to hold the returning
filename and extension. It does not have to be cleared first, since the
routine does this for you, automatically.

Do not make use the SIZEOF function while searching for files with
FINDFIRST and FINDNEXT. Since both routines relocate the DOS Disk Transfer
Address during operation, this may lead to a conflict which will cause
your program to lose track of one or more open files. You should, in any
case, always use the RESETDTA routine to restore the Disk Transfer Address
after FINDFIRST/FINDNEXT is completed.

The DIR$ function which Microsoft have added to Extended QuickBASIC (QBX)
provides a built-in FINDFIRST/FINDNEXT service which makes the Toolbox
routines redundant. They are, therefore, omitted from the BASIC 7 version.


GETDIR

This procedure writes the pathname of the currently logged directory into
the string supplied by the caller. The user can specify what drive to
return the directory for, or default to the current drive.

DECLARE SUB GetDir (Drive%, Path$)

This routine expects two arguments to be passed to it. The first is an
integer which specifies the drive to look at :

0 = default drive, 1 = drive A:, 2 = drive B:, etc.

the second argument is a string which will hold the path of the directory
returned by DOS. The string must be at least 64 bytes long to hold the
information. If it were not, the function might overwrite other variables
in the program data space, with unpredictable results. The returned path-
name does not include the drive identifier or a leading '\' and is
terminated by a null (0) byte. if the current directory is the root
directory, therefore, the first byte of the string will be an ASCII zero,
not a null string.

The CURDIR$ function which Microsoft have added to Extended QuickBASIC
(QBX) allows you to obtain the current directory path and drive, making
GETDIR redundant. It is, therefore, omitted from the BASIC 7 version of
the Assembly Language Toolbox.


GETDRIVE

This function returns the number of the currently-logged drive.

No calling parameters are required.

DECLARE FUNCTION GetDrive% ()

Values returned are in the series 0 = A:, 1 = B:, 2 = C:, etc.

The CURDIR$ function which Microsoft have added to Extended QuickBASIC
(QBX) allows you to obtain the current directory path and drive, making
GETDRIVE redundant. It is, therefore, omitted from the BASIC 7 version of
the Assembly Language Toolbox.


RESETDTA

This procedure must always be called by your program after the FINDFIRST
and FINDNEXT functions have been used. It restores the Disk Transfer
Address to its default value originally set by QuickBASIC.

No calling parameters are required.

DECLARE SUB ReSetDTA ()


SETDRIVE

This function changes the currently-logged drive to the one specified by
the calling program (0 = A:, 1 = B:, etc.).

DECLARE SUB SetDrive (Drive%)

Since BASIC 7 has now introduced the CHDRIVE statement which performs the
same task, SETDRIVE is only supported in the version of the Toolbox
supplied to QuickBASIC 4 users.


──────────────────────────────────────────────────────────────────────

ASSEMBLY-LANGUAGE TOOLBOX INTERNAL FUNCTIONS

The following functions and procedures are used internally by Toolbox
routines. Assembly-Language programmers may also call them when adding
routines of their own, provided the appropriate object modules are linked
to their program at runtime.


FLAGS

Sets or gets the current status of individual flags in the Intra-
Application Communications area (IAC), a 16-byte block of RAM reserved, by
DOS, for signalling between applications programs.

Three parameters must be passed on the stack, they are:

        1)  Switch%     0 = get flag,   1 = set flag
        2)  Flag%       the offset into the IAC flag table (0 to 15)
        3)  Setting%    the value to be set into the specified byte
                        of the flag table (if Switch% = 1).

This example code fragment sets letter 'A' (ASCII 65) into flag 8 (byte 9)
of the IAC area.

            .model  medium              ; Required for QuickBASIC

            extrn   Flags: far          ; Public name of called routine

            .code                       ; Define code segment

            mov     ax,1                ; Set a flag byte
            push    ax                  ; Pass it on the stack
            mov     ax,8                ; Flag number 8
            push    ax                  ; Pass it on the stack
            mov     ax,'A'              ; Value to set
            push    ax                  ; Pass it on the stack
            call    Flags               ; Call the function

You must still push three parameters onto the stack even if you are only
reading a flag setting. In this case the third argument will be ignored.

The setting of the specified IAC flag is returned in the lower byte of the
AX register (AL). All other registers are preserved.


GETVERSION

This function checks the version of DOS under which the host computer is
currently running.

            extrn   GetVersion: far

The following register values may be returned:

    AL      = Major Version       (MS-DOS 3.2 = 3, etc.)
    AH      = Minor Version       (MS-DOS 3.2 = 20, etc.)
    BH      = OEM version number  (0 = IBM PC-DOS)
    BL:CX   = 24-bit OEM serial number.

GETVERSION can be called directly from QuickBASIC, in which case only the
Major and Minor version numbers returned in AX are available.


HIDECURSOR

Makes the cursor invisible. No parameters are required or returned.

            extrn   HideCursor: far

This method ORs the byte value of the cursor start line with 32 (20 Hex)
which, on all standard video adaptors, turns off the cursor while
preserving its display characteristics. You can use the SHOWCURSOR
routine (see below) to restore the cursor to its previous state.

Note:       HIDECURSOR can be called directly from QuickBASIC but, since
            the LOCATE statement provides an alternative means of turning
            off the cursor, it is not necessary.


SCREENADDRESS

Calculate screen address from a pair of row/column co-ordinates.

            extrn   ScreenAddress: far

Given the row/column column co-ordinate of a character on the screen, this
function returns the segment:offset address of that character in video
memory. The address is correctly adjusted to the start of the the
currently active display page, but no check is made to ensure that the
co-ordinates supplied are within the actual screen bounds.

Input:      AL      = Row co-ordinate of character (0 = row 1).
            AH      = Column co-ordinate of character (0 = column 1).

Output:     ES:DI==>  Address in video display buffer of the
                      character cell specified.
            DX      = CRT status register port address.

It is assumed that a previous call has been made to the VIDEOTYPE function
(see below), to determine the screen width, the port address of the CRT
status register and the correct video display segment.


SCREENCOPY

Copy a character and attribute from the video display to a buffer at the
address specified.

            extrn   ScreenCopy: far

If the 'snow prevention' flag is set, this routine waits until the
beginning of the next CRT horizontal retrace period before reading data
from the display. This is necessary only on machines fitted with a Colour
Graphics Adaptor (CGA) which may suffer from glitches or screen snow if
data is copied from the screen while the video buffer is being refreshed.

Input:      DS:SI==>    Address of the screen location from which
                        the data is to be copied.
            ES:DI==>    Address of the buffer into which the data
                        is to be copied.
            DX =        Port address of CRT status register.

Output:     SI and DI   Updated to point to next buffer locations.
            AX          destroyed.

It is assumed that a previous call has been made to the VIDEOTYPE function
(see below), to determine the screen width, the port address of the CRT
status register and the correct video display segment. VIDEOTYPE also sets
an internal 'snow-prevention' flag if the host machine has a CGA display
adaptor installed. This activates a routine which synchronises direct
video reads and writes to the CRT vertical retrace period, preventing
interference on the display.


SCREENREAD

Read a character and attribute from the display.

            extrn   ScreenRead: far

This procedure is similar to SCREENCOPY (see above), except that the word
is simply loaded into AX instead of being copied into a buffer.

Input:      DS:SI==>    address, in the video display buffer, from
                        where the data is to be read
            DX =        port address of the CRT status register.

Output:     AL =        character at the specified address
            AH =        display attribute given to character
            DI          updated to point to the next word address

It is assumed that a previous call has been made to the VIDEOTYPE function
(see below), to determine the screen width, the port address of the CRT
status register and the correct video display segment. VIDEOTYPE also sets
an internal 'snow-prevention' flag if the host machine has a CGA display
adaptor installed. This activates a routine which synchronises direct
video reads and writes to the CRT vertical retrace period, preventing
interference on the display.


SCREENWRITE

Output a character and attribute to the video display.

            extrn   ScreenWrite: far

If the 'snow prevention' flag is set, this routine waits until the
beginning of the next CRT horizontal retrace period before writing data to
the display. This is necessary only on machines fitted with a Colour
Graphics Adaptor (CGA) which may suffer from glitches or screen snow if
data is written to the screen while the video buffer is being refreshed.

Input:      ES:DI==>    Address in the video display buffer where
                        the data is to be written.
            DX =        Port address of CRT status register.
            AL =        Character to output.
            AH =        Display attribute to set

Output:     DI          Updated to point to next output address.

It is assumed that a previous call has been made to the VIDEOTYPE function
(see below), to determine the screen width, the port address of the CRT
status register and the correct video display segment. VIDEOTYPE also sets
an internal 'snow-prevention' flag if the host machine has a CGA display
adaptor installed. This activates a routine which synchronises direct
video reads and writes to the CRT vertical retrace period, preventing
interference on the display.


SHOWCURSOR

Makes the cursor visible. No parameters are required or returned.

            extrn   ShowCursor: far

This method ANDs the byte value of the cursor start line with 31 (1F Hex)
which, restores the cursor after being made invisible by the HIDECURSOR
routine (see above).

Note:       SHOWCURSOR can be called directly from QuickBASIC but, since
            the LOCATE statement provides an alternative means of turning
            the cursor on and off, it is not needed in high-level code.


VIDEO

Video equipment check. This function returns information about the active
display adaptor installed in the host system.

            extrn   Video: far

No input parameters are required, on return AX should be examined for the
following values:

        AL = type of video adaptor installed

             1 = MDA   - Monochrome Display Adaptor
             2 = CGA   - Colour Graphics Adaptor
             3 = HGC   - Hercules Graphics Card
             4 = HGC+  - Hercules Graphics Card Plus
             5 = HIC   - Hercules InColour Card
             6 = EGA   - Extended Graphics Adaptor
             7 = PGA   - Professional Graphics Adaptor (IBM PS/2)
             8 = VGA   - Video Graphics Array
             9 = MCGA  - MultiColour Graphics Adaptor  (IBM PS/2)

        AH  (bits 0-6) = size of display memory in 16K blocks
                         (0 = <16K, 1 = 16K, 2 = 32K, etc.)
            (bit 7)    = type of display monitor in use
                         (0 = colour, 1 = monochrome)


VIDEOTYPE

Collects information about the current video display and sets various
internal flags.

            extrn   VideoType: far

The correct video display segment and CRT status port addresses are
determined for the current system and, if necessary, the internal 'snow'
prevention flag is set.

Input:      nothing

Output:     AL =    Current display mode
            AH =    Screen width in columns
            BL =    Screen height in rows
            BH =    Active display page

You should make a preliminary call to this function before using any of
the other internal routines which directly access video memory.


WRITEBYTE

Output a byte of data to video memory.

            extrn   WriteByte: far

This procedure is similar to ScreenWrite, above, except that only a single
byte is written. It is used by the BackFill routine to reset the display
attribute of a character, without changing the character itself.

Input:      ES:DI==>    address, in the video display buffer, where
                        the byte is to be written.
            DX =        port address of the CRT status register.
            AL =        the byte value to be written.

Output:     DI          updated to point to the next byte address

It is assumed that a previous call has been made to the VIDEOTYPE function
(see above) to determine the screen width, the port address of the CRT
status register and the correct video display segment. VIDEOTYPE also sets
an internal 'snow-prevention' flag if the host machine has a CGA display
adaptor installed. This activates a routine which synchronises direct
video reads and writes to the CRT vertical retrace period, preventing
interference on the display.


─────────────────────────────────────────────────────────────────────────