Black Box 4/BlackBox.cdr/com_term/vtex110.arj/VIDEOTEX.DOC

Text File | 1991-04-17 | 25KB | 516 lines

               VIDEOTEX - Shareware from Powerline Systems Ltd
               -----------------------------------------------

                        Copyright (C) R.T.Russell 1991
                             Release Version 1.00

         REGISTRATION INFORMATION IS PROVIDED AT THE END OF THIS FILE


1. INTRODUCTION

VIDEOTEX is a terminal emulator for the IBM PC, for use in accessing  Videotex
services such as Prestel (TM).  The Videotex screen consists of 24 rows of  40
characters; display attributes, such as colour and graphics, are controlled by
embedded  characters  which  occupy  space on the  screen.   This  format  was
designed to suit hardware implementation and it is difficult to perform a full
emulation in software; this program is designed to provide a 100% emulation.

VIDEOTEX requires an EGA, with at least 128K of RAM, or a VGA.  It is  unusual
in  using  the  512-character-font text mode of the  EGA/VGA  (rather  than  a
graphics  mode)  to achieve the full range of display attributes; it  is  this
that makes it possible to perform a full emulation at a reasonable speed.  All
features  of  the  Videotex display are supported: colour  text  and  graphics
(contiguous  and separated), background colour, flashing, double-height  (text
and graphics), held-graphics (for abrupt colour changes) and concealed text.

The  full  Videotex  (UK) character set is supported.   Those  characters  not
having an equivalent in the ASCII set are obtained from the following keys:

     left arrow          [         long dash        _ (underscore)
     right arrow         ]         divide sign      ~ (tilde)
     up arrow            ^         double bar       |
     one half            \         small block      CTRL-2 or CTRL-backspace
     one quarter         {         pound sign       ` or £
     three quarters      }

VIDEOTEX is believed to be bug free... isn't all software!  If you do find any
problems please TELL US using the methods given at the end of this file.


2. INSTALLATION

VIDEOTEX  consists  of the single executable file VIDEOTEX.EXE,  it  needs  no
installation.  The only options are controlled by the command line:

            VIDEOTEX [/b:baud] [/c:port] [dialstring][@scriptfile]

   /b:baud  Controls  the speed to which the serial port will be set.   'baud'
            may be one of the following values: 75, 150, 300, 600, 1200, 2400,
            4800,  9600,  19200  or  38400.  For  example,  /b:2400  sets  the
            transmit  and  receive speeds to 2400 baud.  If the /b  switch  is
            omitted the speed defaults to 9600 baud.
            V23 (75 TRANSMIT, 1200 RECEIVE) IS NOT CURRENTLY IMPLEMENTED.

   /c:port  Determines which serial port (COM1 or COM2) is used.  For example,
            /c:2 selects port COM2.  If omitted the port defaults to COM1.
            PORTS COM3 AND COM4 ARE NOT CURRENTLY SUPPORTED.

dialstring  An  optional  character string which will be processed  as  though
            typed  at the keyboard.  Note that the string may not contain  the
            characters  /,  <, >, @ or |.  If any of these are needed,  use  a
            script file containing the required string.

scriptfile  A  file  whose contents will be processed as though typed  at  the
            keyboard;  when the end-of-file is reached, the keyboard  will  be
            activated as usual.  Control codes are ignored, so the file may be
            split into separate lines to aid readability.

The  tilde  character (~) can be used in the dial string and script  files  to
allow  control characters and terminal commands to be  incorporated.   Control
characters are generated by ~ followed by an UPPER CASE letter: for example ~M
represents   the  carriage  return  character.   Terminal  commands   may   be
incorporated as ~a to ~z, corresponding to ALT-A to ALT-Z respectively.  Other
codes which may be used are  ~? to send the DEL character (7F) and ~~ to  send
the ~ character itself.  See below for more details of script files.

You  can create batch files to access your favourite Videotex  services.   For
example, the file PRESTEL.BAT might contain the following line:

         VIDEOTEX /B:2400 /C:2 ~o~M~wATDT0716181111~M~i44444444444444

The MAKEBAT utility has been provided to simplify producing such files.


3. OPERATION

When  the  unregistered version of VIDEOTEX is executed an initial  banner  is
displayed  for five seconds or until a key is pressed (the registered  version
does not display this banner).  You are then presented with a 40-column by 25-
row  screen,  where  the  bottom row is a  permanent  status  line.   VIDEOTEX
initialises to the Offline state: press ALT-O to go online.

All  the  alphanumeric keys generate the normal codes (see above  for  special
characters).  Control codes are sent conventionally: for example CTRL-L (clear
screen)  or  CTRL-^ (home cursor) may be sent to an online  editor.   ESC  and
RETURN generate the standard codes.

The 'arrow' keys generate the appropriate cursor-movement codes and the  other
special keys are pre-programmed with character sequences to suit Prestel:

                    Home      *0#       (go to index page)
                    End       *90#      (leave Prestel)
                    PgUp      *#        (recall previous page)
                    PgDn      #         (enter / next page)

                    Backspace           (delete previous character)
                    Tab                 (tabulate)
                    SHIFT-Tab           (back-tab)

                    Ins       ESC i     (insert character)
                    Del       ESC d     (delete character)
                    CTRL <-   ESC b     (word left)
                    CTRL ->   ESC f     (word right)
                    CTRL Home ESC K     (edit start)
                    CTRL End  ESC J     (edit end)


Function keys:

The  function  keys, in conjunction with SHIFT and CTRL, can be used  to  send
attribute  codes to line (or direct to the screen if in Offline  mode).   Some
response frames do not allow all these codes to be used.

               normal              with SHIFT          with CTRL

     F1        alpha red           graphics red        separated graphics
     F2        alpha green         graphics green      contiguous graphics
     F3        alpha yellow        graphics yellow     hold graphics
     F4        alpha blue          graphics blue       release graphics
     F5        alpha magenta       graphics magenta
     F6        alpha cyan          graphics cyan
     F7        alpha white         graphics white
     F8        flash               steady
     F9        new background      black background
    F10        double height       normal height       conceal


The carousel:

A carousel of previously-viewed frames is kept in memory; if the memory  fills
the  oldest frame in the carousel is overwritten.  When the current  frame  is
cleared from the screen (by receipt of the CTRL-L code) it is first written to
the carousel; note that if the frame is cleared by another method (for example
recalling another frame from disk) then it is not stored in the carousel.

The  contents  of  the carousel may be reviewed, when in  offline  mode,  (see
section 5) or may be saved to disk (ALT-F).  There is no command to clear  the
carousel,  but this may be achieved by loading the carousel from the NUL  file
(ALT-G).


Mailbox editing:

Mailbox messages can be prepared off-line to save time and telephone  charges.
To  do  this  you should first save to disk the  empty  mailbox  frame  (ALT-S
command);  this need only be done once.  When offline you can then  load  this
frame  (ALT-L),  add/edit your message and save the completed frame  to  disk.
Take  care to enter your text only within the area provided for  the  message,
and  avoid use of the # character.  Several different frames may  be  prepared
this way, each saved to disk with a different filename.

When next online, go to the page containing the blank mailbox frame which  you
previously saved.  When this frame is displayed, with the cursor at the  first
location  of the message area, recall the filled-in frame from  disk  (ALT-L).
Transmit the frame using the ALT-T command, if all is well your message should
be  transferred  to the remote host; if necessary use *00 to  check  it.   The
usual prompts should then be followed to send the message.

If  the message is corrupted, for example because of line noise, then  re-load
the  frame from disk and try again.  Some response frames initially  move  the
cursor by two spaces, which can cause the transmitted frame to be shifted;  if
this is a problem press right-arrow then left-arrow before issuing the ALT-T.


Script language:

A  simple script language is provided to allow automation of some  operations,
such  as logging onto Prestel, downloading a number of frames and logging  off
again.   The  script  language  has only three  commands,  each  of  which  is
introduced by the ~ (tilde) character:

          ~{        Start a block
          ~}        End a block
          ~|<expr>  Exit from a block if <expr> is true

The  contents  of a script file between a start-block code  and  an  end-block
code are repeated indefinitely.  In other words, on encountering an  end-block
code a 'jump' to the matching start-block code is made.  The only way to leave
a  block  (other than with CTRL-BREAK) is with the exit-block  code;  this  is
followed by a conditional expression which can evaluate to TRUE or FALSE.   If
FALSE,  execution continues after the exit-block command; if TRUE, a  jump  is
made to the end-block code and execution continues after this.  Blocks may  be
nested to a depth of nine levels.  An exit-block code not within a block  will
cause termination of the script file if the condition is TRUE.

The  only  conditional  test  currently provided is  for  the  presence  of  a
specified string on the screen.  This is indicated by enclosing the string  in
double quotes, for example the command:

          ~|"Hello"

will exit the current block if the string "Hello" is displayed anywhere on the
screen,  otherwise  execution  will continue.  The sense of the  test  may  be
reversed by prefixing the expression with ! (signifying NOT), for example:

          ~|!"Hello"

will  exit  the block if the string "Hello" is NOT displayed.   Tests  may  be
combined  with the logical | (OR) and & (AND) operators, but in this case  the
entire expression must be enclosed in parentheses, for example:

          ~|("Hello"&"there")

will  exit  the  block  if both "Hello" and "there"  are  displayed.   The  OR
operator may be used to cope with uncertainties about spelling etc., e.g.:

          ~|("Hello"|"hello"|"HELLO")

A  null  string ("") is always TRUE so this can be used for  an  unconditional
jump.  For example, comments may be included using the following syntax:

      ~{~|"" The unconditional exit causes this comment to be skipped ~}

REPEAT...UNTIL,   WHILE...DO and IF...THEN constructs can be  fabricated  from
the primitive commands as follows:

     ~{<operation>~|<condition>~}       REPEAT <operation> UNTIL <condition>

     ~{~|!<condition><operation>~}      WHILE <condition> DO <operation>

     ~{~|!<condition><operation>~|""~}  IF <condition> THEN <operation>


4. TERMINAL FUNCTIONS

  ALT-A  Awaits a receive timeout.  For use in script files.

  ALT-B  Sends a 'break', of approximately 0.2 seconds, to the serial output.

  ALT-C  Show  codes:  disables  the action of all  attribute  characters  and
         instead displays them as special two-letter symbols, as follows:

               NU   NUL *               DL   DLE *
               AR   alpha red           GR   graphics red
               AG   alpha green         GG   graphics green
               AY   alpha yellow        GY   graphics yellow
               AB   alpha blue          GB   graphics blue
               AM   alpha magenta       GM   graphics magenta
               AC   alpha cyan          GC   graphics cyan
               AW   alpha white         GW   graphics white
               FL   flash               CD   conceal display
               ST   steady              CG   contiguous graphics
               EB   end box *           SG   separated graphics
               SB   start box *         EC   ESC *
               NH   normal height       BB   black background
               DH   double height       NB   new background
               SO   shift out *         HG   hold graphics
               SI   shift in *          RG   release graphics

         *  these symbols correspond to undefined escape sequences and  should
         not  normally  be seen.  They relate to the  stored  attribute  codes
         rather than the characters received; e.g. NUL results from ESC @.

         The  status  line  is replaced by a list of these  symbols,  in  code
         order, as an 'aide memoire'.  In this mode, any characters which were
         received with a parity error (odd parity rather than even parity) are
         displayed on a red background.  Press any key to exit this mode.

  ALT-D  Telesoftware  download.   Should  be entered  when  the  telesoftware
         'header' frame is displayed, to initiate transfer of CET-encoded data
         to  a  disk file on your machine.  You are prompted for  a  filename,
         which defaults to that given in the 'header'; press RETURN to  accept
         that filename, or enter another.  To abort the command press ESC;  to
         abort the download once started press CTRL-BREAK (this may result  in
         an incomplete file being left on your disk).

  ALT-E  Erases  a  file from the disk.  You are prompted  for  the  filename:
         wildcards are not allowed.  To abort the operation press ESC.

  ALT-F  Files  (saves) the carousel.  You are prompted for a filename;  press
         RETURN when it has been entered.  To abort the operation press ESC.

  ALT-G  Gets (loads) a saved carousel. You are prompted for a filename; press
         RETURN when it has been entered.  To abort the operation press ESC.

  ALT-H  Calls up a 'help' page.  Press any key to return to normal.

  ALT-I  Waits  until receipt of the ENQ character, or a local  keypress  (for
         use in script files).  May be aborted with CTRL/BREAK.

  ALT-K  Programs a user-defined key.  The key combinations ALT-0 to ALT-9 can
         be  programmed to produce user-defined character sequences.  You  are
         prompted  for the key to define (0-9) and for the string you wish  to
         place in the key: press RETURN to enter the string.  The total length
         of the strings in all the user-defined keys is limited to 240 bytes.

  ALT-L  Loads  the  screen from a file.  You are prompted for  the  filename;
         press RETURN when it has been entered.  To abort the load press ESC.

  ALT-N  Pulses  the DTR line for approximately 0.2 seconds, which will  cause
         most modems to hang-up the telephone line.

  ALT-O  Toggles between online (remote) and offline (local) operation.   When
         offline  the status line shows the message 'Offline'  and  everything
         entered  at the keyboard is sent to the local display rather than  to
         line.  Characters received whilst offline will still be displayed.

  ALT-P  Prints  the  currently  displayed  frame.   Requires  an  Epson  FX80
         printer, or compatible, connected to the LPT1 port (which may be  re-
         directed using the DOS MODE command).  To abort the print press CTRL-
         BREAK;  however, if your printer is not connected or is switched  off
         the program may not respond.

  ALT-Q  Quits  from the program, and sets the RTS and DTR lines  inactive  to
         hang-up  the telephone line.  You are prompted for confirmation;  any
         character other than Y will abort the exit.

  ALT-R  Reveals any concealed text. This key has a toggle action: pressing it
         again  conceals  the  text.   Receipt of  a  clear  screen  character
         establishes the 'concealed' state.

  ALT-S  Saves the displayed frame to a file. You are prompted for a filename;
         press RETURN when it has been entered.  To abort the save press ESC.

  ALT-T  Transmits the currently displayed frame to line.  This operation  has
         two  modes, depending on the initial cursor position.  If the  cursor
         is in the 'home' location (top left corner of the screen) the  entire
         frame  is  sent,  with  trailing spaces  being  converted  to  CR  LF
         sequences.  If the cursor is not in the 'home' location, the  portion
         of the frame from the cursor position to the next # character (or  to
         the  end  of the frame if there are no # characters)  will  be  sent;
         trailing spaces are not converted to CR LFs.

  ALT-U  Uploads a file; ~ sequences within the file will be processed as  for
         a script file.  You are prompted for a filename, press ESC to abort.

  ALT-V  Views  the  disk directory.  All files in the current  directory  are
         listed;  if the screen fills the program waits for a keypress  before
         scrolling the display.  Press any key to return to normal.

  ALT-W  Pauses  for  one second.  This is primarily intended for  use  within
         script files, and is not generally very useful from the keyboard.

  ALT-Y  Changes  the current disk drive or directory.  If a drive name  alone
         is  entered (e.g. A:) the default drive is changed.  If  a  directory
         path is entered, the current directory is changed.


5. OFFLINE EDITING

When  the terminal is offline, frames may be edited locally.  A frame  can  be
loaded from disk with the ALT-L command, edited, then saved back to disk  with
the ALT-S command.  The following keys are active in this mode:

left arrow   Moves the cursor left one character.

right arrow  Moves the cursor right one character.

down arrow   Moves the cursor down one line.

up arrow     Moves the cursor up one line.

Tab          Moves the cursor right to the next 8-character-wide column.

SHIFT-Tab    Moves the cursor left to the previous 8-character-wide column.

CTRL <-      Moves the cursor left until it is at the start of a word.

CTRL ->      Moves the cursor right until it is after the end of a word.

RETURN       Moves the cursor to the start of the line.

Backspace    Deletes the character to the left of the cursor.

Ins          Inserts  a space at the cursor position.  All characters  to  the
             right of the cursor are moved right.  The last character is lost.

Del          Deletes the character at the cursor position.  All characters  to
             the right of the cursor are moved left one place.

CTRL PgDn    Inserts a blank line at the cursor position.  All lines below the
             cursor are moved down.  The bottom line is lost.

CTRL PgUp    Deletes  the  line containing the cursor.  All  lines  below  the
             cursor are moved up.

Home         Moves to and recalls the first frame in the carousel.

End          Moves to and recalls the last frame in the carousel.

PgUp         Moves back one frame in the carousel.

PgDn         Moves forward one frame in the carousel.

CTRL L       Writes the frame to the carousel, then clears the screen.

CTRL ^       Moves the cursor to the top-left (home) position.

CTRL Q       Turns on the cursor.

CTRL T       Turns off the cursor.

ESC o        Turns off the colour/word wrapping mode.

ESC w        Turns on the colour/word wrapping mode.


6. ERROR MESSAGES

If an error occurs a flashing message will appear in the centre of the screen;
press any key to clear this message.  The possible messages are as follows:

Access denied      A  file could not be created or opened (e.g. an attempt  to
                   create a new file with the same name as a read-only file).

Bad directory      The specified disk drive/directory does not exist.

Break rcvd         A  'break'  condition was detected on the  incoming  serial
                   data.  This should not normally occur.

Device fault       A device fault occurred, e.g. while printing a frame.

Disk fault         The disk is faulty, e.g. unformatted or not inserted.

Disk full          The output file cannot be written because the disk is full.

Disk read only     The  file  cannot be written, because the  disk  is  write-
                   protected.

Download fault     An  irrecoverable download error occurred,  e.g.  incorrect
                   number of frames or maximum retries exceeded.

File not found     An attempt was made to read a file which does not exist.

File system error  A miscellaneous filing system (i.e. disk) error occurred.

Handshake?         The  receive  buffer has overflowed, owing  to  failure  of
                   hardware  (RTS) and/or XON-XOFF  handshaking.   Handshaking
                   should only be required at very high data rates.

Invalid header     The  Download command was issued but no valid  telesoftware
                   header  frame is displayed.  If necessary,  re-display  the
                   frame with *00.

Nested too deep    Blocks in a script file are nested more than nine deep.

RX framing         A  framing error was detected on the incoming serial  data.
                   This may indicate that the baud rate is incorrectly set.

RX overrun         An incoming data byte was lost.  This can be caused by  the
                   KEYB  utility  which disables interrupts  for  an  extended
                   period.   A  replacement KEYB routine is available  if  you
                   find this to be a problem.

RX parity          A  parity error was detected on the incoming  serial  data.
                   As checking is disabled, this error should not occur.

Script syntax      A script file command cannot be understood.

TX timeout         A  character  could  not  be sent  to  the  serial  output.
                   Probably  caused by the CTS handshaking line being  low  or
                   disconnected.  Check the wiring of your modem connection.

User abort         The user has pressed CTRL-BREAK to abort an operation.


7. REGISTRATION

This  program  is *ShareWare*, NOT public domain or free  software.   You  may
freely  share it with friends and upload it to Bulletin Boards but only  in  a
completely  unmodified form including all the original program,  documentation
and  support  files.  No charge or payment may be levied or accepted  and  the
program  may not be distributed as part of a commercial product other than  by
prior arrangement with the author.

If  you find this program useful please register it and support the  Shareware
concept.   Registered users can obtain technical support from the  Direct-Line
Online  System or from the PC SUPPORT area on Prestel.  To register your  copy
of the program please send a cheque or postal order for £20 to:

                              Powerline Systems Ltd
                              44 Rydal Way
                              Ruislip
                              Middlesex
                              HA4 0RU

Cheques  should be made payable to 'Powerline Systems Ltd'; please state  your
name  and  address on the back of the cheque or in a letter  accompanying  it.
You  will  be  sent a unique registration number to  enter  via  the  REGISTER
program to register your copy of VIDEOTEX.  Once registered to you the program
MUST  NOT  be  passed on to others; only Shareware copies may  be  passed  on.
Registered versions do not display the Shareware banner displayed by the  non-
registered version.


Feedback on this program is welcomed via the Direct-Line Online System or  the
PC Support area on Prestel/Micronet (key *PC SUPPORT#).  Direct-Line  operates
on the following London numbers (set your communications software for 8/N/1):

          081-841 1847   Speeds  300/1200/1200-75/2400  MNP5
          081-842 2030   Speeds  300/1200/2400/V32(9600)+14.4K HST  MNP5
          081-842 4176   Speeds  300/1200/1200-75/2400

Latest versions are ALWAYS available for download from Direct-Line.  They  are
also  placed  in  the UKFORUM area on Compuserve  for  worldwide  access.   We
welcome suggestions for enhancements to the program.


Please  note  that although this software is thought to be free  from  serious
bugs,  and  it is highly unlikely it could do any harm to  other  software  or
systems,  there  is NO warranty that it will not and all use is  at  your  own
risk.


      Copyright (C) Richard Russell & Powerline Systems Ltd.  April 1991