Gold Medal Software 2/Gold Medal Software Volume 2 (Gold Medal) (1994).iso/prog/asm_0_m.arj/HBUILD16.ASM

Assembly Source File | 1986-04-07 | 21KB | 653 lines

TITLE    HBUILD VERSION 1.60    16 December 1985
Page    ,132
COMMENT #
                HBUILD VERSION 1.60

    This is a universal help program engine that enables an    indexed
    help program to be constructed from the HBUILD.COM file and a
    suitably formatted text file.

    The text of the help file which is used as input to this program
    must be formatted according to a set of exact criteria. It is
    important that no errors be made in the layout, as, while I have
    included some error trapping, it is not totally bulletproof.

    The first character to appear in the file is used by the program
    as the separation character that it will look for in the rest of the
    help file to indicate the end of a piece of text. This should be a
    character that you will NOT use anywhere else in the help text.
    I usually use the "happy face" (^A = ASCII 01) which my word processor
    allows me to insert in a text file. The separation character must
    appear as the first character in the help file followed immediately
    by a CR and LF. The next character, again immediately followed by a
    CR and LF is the exit character. This is the character which when
    typed in response to any prompt and followed by a RETURN will exit
    the program.

    The format of the help file is as follows (using @ as the separation
    character and * as the exit character, so they will display easily on
    your word processor) :
@
*
MENU
User prompt for the first screen (placed on line 25)
This will be the text of the first screen which will contain
a list of help topics that can be requested. The data on this
screen is for user information only. The program doesn't use
anything here for index purposes. You may write any text here.
Other screens can be used as sub-menu
This is a list of commands:

        COMMAND 1
        COMMAND 2
        etc ...

@
COMMAND 1
User prompt that appears on COMMAND 1 topic screen on line 25
            \70 COMMAND 1 TITLE IN REVERSE VIDEO \07

This is the help text for "COMMAND 1" which may be up to 24 lines of data
starting at the line immediately follwing the 9 characters of "COMMAND 1".
@
COMMAND 2
User prompt that appears on COMMAND 2 topic screen on line 25
                \01 COMMAND TWO \07

This is the help text for "COMMAND 2", whose title is this time shown as
underlined on a monochrome screen, or in blue on a color screen. This will
be the last command as it is followed by two separation characters on separate
lines.
@
@

    Each command that is to be recognised by the help program MUST
    occupy exactly 9 characters (pad on the right with blanks as needed),
    be in UPPER CASE and be followed immediately by a CR and an LF.
    The prompt for that help screen, which will be located on line 25,
    follows immediately after the command, and should be 70 characters or
    less. The help text immediately follows the prompt and may be up to 24
    screen lines long. The text can contain embedded codes to change the
    attribute of the characters being written. These are entered with a
    backslash followed by TWO (must be two) hex digits which specify the
    color/attribute of the characters which follow,    until a new embedded
    code appears. For example \70 TITLE \07 if it appeared in the help
    text would display "TITLE" and the spaces either side of it in reverse
    video, and subsequent text in regular video. A backslash character
    can be inserted in the text using \\. Tabs are expanded and CR/LF
    combinations are properly interpreted. The whole help text MUST be
    terminated with TWO separation characters following each other on
    separate lines. Note that the commands MUST be placed in the help file
    in alphabetical order, if entries are going to be able to be found
    where the entry characters are the same e.g. the command PRINT will
    only be found if it preceeds the command PRINTER in the help text.

    To make the help program from the help text, run HBUILD with the
    following syntax:

    HBUILD * [D:][PATH]HELPTEXT.EXT [D:][PATH]PROGNAME.COM

    This will cause HBUILD to load the file HELPTEXT.EXT into memory,
    index the commands and then, if there are no errors in the format
    of the help text, write a file called PROGNAME.COM. If drive and
    path are not specified then HBUILD will use the default drive and
    directory.

    PROGNAME.COM then contains the HBUILD "help engine" with the indexed
    contents of HELPTEXT.EXT attached to it in the same file. To use
    PROGNAME.COM, simply type :

    PROGNAME [TOPIC]

    at the DOS prompt, and you will be presented with the help screen
    indexed to the command TOPIC (if it was included on the DOS command
    line). If the help topic was not included on the command line, or    the
    name supplied does not appear in the index in PROGNAME, then you will
    be presented with the screen defined at the head of the help text,
    which should include a list of available commands.

    The command interpreter will match on less than the total number
    of characters in the command typed in at the prompt (or at the
    command line), and will find the FIRST command that matches those
    characters input; case is ignored. For example if the help text
    contains the commands DISKCOMP and DISKCOPY, then the user input
    DISKC will find DISKCOMP (assuming the help text had them in
    alphabetical order). The user input of DISKCOP will find DISKCOPY.
    To terminate the program you can press the ENTER key with no input.

    Note that PROGNAME.COM contains the same program code as the
    original HBUILD.COM file, so if you want, you could use PROGNAME
    to update itself with a command like:

    PROGNAME * HELPTEXT.MOD PROGNAME.COM


                    David Gwillim
                    1414 N. Catalina Street
                    Los Angeles  CA 90027
                    16 December 1985

#
;
IF1
    %OUT    ************
    %OUT    * Pass One *
    %OUT    ************
ENDIF

IF2
    %OUT
    %OUT    ************
    %OUT    * Pass Two *
    %OUT    ************
ENDIF

LF    EQU    0AH
CR    EQU    0DH
CRTMode    EQU    449H            ;ROM BIOS data area address
MaxSize    EQU    65400            ;Base figure for help text size
                    ; computation (allows 135 bytes
                    ; for stack space)
Cseg    SEGMENT
    ASSUME CS:Cseg,DS:Cseg,ES:Cseg,SS:Cseg
    ORG    100H

Start:    Mov    AH,30H            ;Check DOS version
    Int    21H
    Cmp    AL,2            ;Version 2 or greater?
    Jnl    H00
    Mov    DX,Offset BadDos    ;Print wrong DOS message
    Call    PText
    Mov    AX,4C01H        ;Set error code & terminate process
    Int    21H

H00:    Sub    AX,AX            ;Make a zero
    Mov    DS,AX            ;Point to ABS0 segment
    Mov    SI,CRTMode        ;Point to CRTMode byte
    Lodsb
    Cmp    AL,7            ;Mode 7 = Monochrome screen?
    Jne    H0            ; if no, use color default
    Mov    ScrnAdd,0B000H        ;Point to monochrome screen memory
H0:    Push    CS
    Pop    DS
    Mov    SI,81H            ;Point to DOS command tail
H1:    Lodsb
    Cmp    AL,' '            ;Skip any blanks
    Je    H1
    Cmp    AL,'*'            ;Check for build option
    Jne    H2
    Jmp    BuildHelp        ;We are making a help file
H2:    Cmp    AL,CR            ;Any command tail?
    Je    H5            ;If no, go interactive
    Mov    DI,Offset Cmd        ;Place to store command tail
    Mov    CX,9            ;Transfer 9 characters maximum
H3:    Cmp    AL,CR            ;Transfer command tail
    Je    H4
    Inc    CmdLen
    Stosb
    Lodsb
    Loop    H3
H4:    Call    GC0            ;Jump into middle of GetCmd
    Jmp    H8            ;Display help text
H5:    Mov    DX,Current        ;Select current screen
H6:    Call    PHelp            ;Display help text
H7:    Call    GetCmd            ;Get next command
    Cmp    CmdLen,0        ;Just a <RETURN> entered?
    Je    H5
    Cmp    CmdLen,1        ;Single character input line?
    Jne    H8            ; if so, exit program
    Mov    AL,Cmd            ;What's the character that was input?
    Cmp    AL,ExitChr        ;Is it the exit character?
    Jne    H8
    Call    ClrScr            ;Clean up the screen before we leave
    Mov    AX,4C00H        ;Set error code & terminate process
    Int    21H
H8:    Call    GetMatch        ;Find offset to help text
    Cmp    DX,0            ;Help text found?
    Je    H5            ;If not get another command
    Mov    Current,DX        ;Command found, print it
    Jmp    H6            ;Do it all over again

; Clear screen
%OUT    -    ClrScr
ClrScr    proc    near
    Mov    BH,07            ;Clear screen with NORMAL attribute
    MOV    AX,0600H        ; using "scroll active page up"
    MOV    CX,0            ; Upper left corner coords (0,0)
    MOV    DX,184FH        ; Lower right corner coords (79,24)
    INT    10H
    MOV    AH,2            ;Set cursor position
    MOV    BH,0            ;Page 0
    MOV    DX,0H            ;Coords (0,0)
    INT    10H
    Mov    ScrnPos,0        ;Point to beginning of the screen
    RET
ClrScr    endp

;    Get the input command from the user
%OUT    -    GetCmd
GetCmd    proc    near
    Mov    DI,Offset CmdLen    ;Initialize buffer to zeros
    Mov    AL,0
    Mov    CX,10
    Rep    Stosb
    Mov    DX,Offset CmdBuff    ;Point to command input buffer
    Mov    AH,0AH            ;Request edited input from DOS
    Int    21H
GC0:    Sub    CX,CX            ;Zero out CX
    Mov    CL,CmdLen        ;Get input command length
    Inc    CX            ;To permit handling null input
    Mov    SI,Offset Cmd        ;Point to input command
    Mov    DI,SI            ; for Lodsb and Stosb
GC1:    Lodsb                ;Get the next char from Cmd string
    Cmp    AL,'a'            ;Upper case any lower case characters
    Jl    GC2
    Cmp    AL,'z'
    Jg    GC2
    And    AL,5FH
    Cmp    AL,CR            ;End of input line?
    Jne    GC2
    Mov    AL,0            ;Terminate input with a 0 byte
GC2:    Stosb
    Loop    GC1
    Ret
GetCmd    endp

;    Print prompt for next command
%OUT    -    PPrompt
;Entry: DX contains offset to prompt string terminated in a 0 byte
PPrompt    proc near
    Mov    ScrnPos,3840        ;Point to cursor position (0,24)
    Call    FText            ;Print the prompt
    Push    DX            ;Save returned pointer to help text
    MOV    BH,0            ; on page 0
    MOV    DH,18H            ; to row 24
    Mov    AX,ScrnPos        ;Get last screen location printed + 1
    Sub    AX,3840            ;Get # bytes into row 24
    Shr    AX,1            ;Divide by 2 to get cursor position
    Mov    DL,AL            ; and put cursor there
    MOV    AH,2            ;Set cursor position
    INT    10H
    Mov    ScrnPos,0        ;Point to the top of the screen again
    Pop    DX            ;Restore pointer to help text
    RET
PPrompt    endp

%OUT    -    GetMatch
GetMatch    proc    near
    Mov    BX,HelpTxt        ;Point to start of command table
    Mov    DX,0            ;Initialize DX
GM1:    Cmp    BX,0            ;Pointer to next command in table = 0?
    Je    GM3            ;if so, we are at the end of the table
    Mov    DI,BX            ;Store start offset of command
    Sub    CX,CX            ;Zero out CX
    MOV    CL,CmdLen        ;Retrieve length of entered command
    MOV    SI,Offset Cmd        ;Point to entered command
    REPZ    CMPSB            ;Compare them
    Jne    GM2            ;If they weren't equal, try next cmd
    Add    BX,11            ;Jump over the command and pointer
    MOV    DX,BX            ;This is the address of the prompt
GM2:    CMP    DX,0            ;Was there a match?
    Jne    GM3            ;If yes, then return
    Mov    BX,[BX+9]        ;Get pointer to start of next command
    Jmp    GM1            ;Go check for a match with it
GM3:    RET
GetMatch    endp

%OUT    -    PHelp
PHelp    proc near
    PUSH    DX            ;Save the offset to the prompt
    CALL    ClrScr            ;Clear the screen
    POP    DX            ;Restore the offset to the prompt
    Call    PPrompt            ;Print prompt for next command
    Inc    DX            ;Point DX to help text
    CALL    FText            ;Display the help text
PH1:    RET
PHelp    endp

;Print a piece of text
;Entry: DX points to start of text which is terminated in a 0 byte
;Exit : DX points to byte following 0 terminating byte
%OUT    -    FText
FText    proc    near
    Mov    SI,DX            ;Point to text string with SI
    Mov    DI,ScrnPos        ;Pick up the current screen position
    Push    ES            ;Save ES
    Mov    ES,ScrnAdd        ;Point ES to current screen memory
    Mov    AH,7            ;Default attribute
    Mov    CX,0            ;Start in column 0
PutScr:    Lodsb                ;Get byte from Buffer
    Cmp    AL,0            ;End of text?
    Je    Out
    Cmp    AL,'\'            ;Is this a change of attribute
    Jne    L3
    Call    GetAttrib        ;Read the next byte as new attribute
    Jmp    PutScr
L3:    Cmp    AL,CR            ;Is it a CR
    Jne    L3A
    Call    Pad            ;If so pad to end of line with blanks
    Jmp    PutScr
L3A:    Cmp    AL,9            ;Is it a tab character
    Jne    L4
    Call    FExpandTab        ;If so, expand it (8 space column)
    Jmp    PutScr
L4:    Cmp    AL,LF
    Je    PutScr            ;Ignore line feeds
ToScr:    Stosw
    Inc    CH            ;Keep track of column position
    Jmp    PutScr
Out:    Mov    ScrnPos,DI        ;Store screen position
    Pop    ES            ;Restore ES register
    Mov    DX,SI            ;Return next position in text
    Ret
FText    endp

%OUT    -    FExpandTab
FExpandTab    proc near
    Push    AX            ;Save current attribute
    Cmp    CH,71            ;Are we in column 72 or more?
    Jg    FET2            ; if so just do a CR,LF
    Mov    AX,CX            ;Put the column position in AL
    XChg    AH,AL
    Sub    AH,AH
    Cmp    AL,0            ;Make sure no divide by zero!
    Je    FET1
    Div    Eight            ;Find out how far past last tab col
FET1:    Xchg    AH,AL            ;Compute number of spaces to next
    Mov    AH,8
    Sub    AH,AL
    Add    CH,AH            ;Keep track of line position
    Mov    CL,AH            ;Number of spaces to print
    Pop    AX            ;Get attribute byte
    Push    CX            ;Save current value of line pos
    Sub    CH,CH            ;Store count of spaces to display
    Mov    AL,' '            ;Space character
    Rep    Stosw            ;Write to the screen
    Pop    CX            ;Restore CX
    Ret
FET2:    Pop    AX
    Call    Pad            ;Pad line out to 80 columns
    Ret
FExpandTab    endp

%OUT    -    Pad
Pad    Proc    Near
    Mov    CL,80
    Sub    CL,CH            ;Compute how many columns left
    Je    EndPad            ;If zero we are in column 80.
    Sub    CH,CH            ;So we can add CL to DI
    Shl    CX,1            ;Double CX to allow for attribute byte
    Add    DI,CX            ;Pad columns to 80 by incrementing DI
EndPad:    Sub    CH,CH            ;Reset column position counter to 0
    Ret
Pad    Endp

%OUT    -    GetAttrib
GetAttrib    proc    near
    Push    CX            ;Save CX register
    Push    AX            ;Save current attribute in AH
    Sub    AH,AH            ;Start with 0 in AH
    Mov    CX,2            ;Accept 2 hex digits only
GA1:    Lodsb                ;Treat next character as attribute
    Cmp    AL,'\'
    Je    Literal            ;Another \ treat as a literal char
    Sub    AL,30H            ;Make ASCII digit binary
    Jl    GAOut            ;Check if too low
    Cmp    AL,9
    Jle    GA2
    And    AL,5FH            ;It wasn't 0 - 9 so upper case it
    Sub    AL,7            ;Make A - F into binary 10 - 15
    Cmp    AL,10            ;Less than A?
    Jl    GAOut            ;Too low for A - F
    Cmp    AL,15            ;Greater than F?
    Jg    GAOut
GA2:    Add    AH,AL            ;Accumulate hex digit
    Cmp    CX,2            ;Is this the first digit
    Jne    GA3
    Push    CX            ;First hex digit so multiply by 16
    Mov    CL,4
    Shl    AH,CL
    Pop    CX
    Loop    GA1            ;Get the 2nd digit
GA3:    Pop    CX            ;Throw away saved AX register
    Pop    CX            ;Restore original CX register
    Mov    AL,0            ;Signify satifactory conversion
    Ret                ;AH contains new character attribute

GAOut:    Pop    AX            ;If get here was an invalid hex number
    Pop    CX            ; or a literal '\'
    Ret
Literal:
    Pop    AX            ;Restore registers
    Pop    CX
    Stosw                ;Put a \ to the screen
    Inc    CH            ;Keep track of column position
    Ret
GetAttrib    Endp

%OUT     -    BuildHelp
BuildHelp:
    Call    GetNames        ;Get the file names for build
    Mov    DX,Offset Author    ;Print copyright
    Call    PText
    Mov    DX,Offset BHMsg        ;Tell user we are doing build
    Call    PText
    Call    LoadTxt            ;Load help text into memory
    Call    SaveFile        ;Index the text & save it as a pgm
    Mov    DX,Offset BHDone    ;Tell user we are donw
    Call    PText
    Mov    AX,4C00H        ;Set error code & terminate process
    Int    21H

;Print a piece of text
;Entry: DX points to start of text which is terminated in a 0 byte
%OUT    -    PText
PText    proc    near
    MOV    SI,DX            ;Pointer to text start
PT1:    Lodsb
    Cmp    AL,0            ;Are we at the end of the text?
    Je    PT3
;    Cmp    AL,9            ;Tab character
;    Jne    PT2
;    Call    ExpandTab        ;Expand the tab to spaces
;    Jmp    PT1
PT2:    Mov    BL,7            ;Normal foreground color
    Mov    AH,0EH            ;Write teletype function
    Int    10H
    Jmp    PT1
PT3:    RET
PText    endp

%OUT    -    GetNames
GetNames    proc near
    Mov    DI,Offset InName    ;Point to 1st name buffer
GN1:    Lodsb                ;Skip any leading spaces
    Cmp    AL,' '
    Je    GN1
GN2:    Cmp    AL,CR            ;End of command tail
    Je    GNErr            ; if so error - no 2nd name
    Cmp    AL,' '            ;Space means end of 1st name
    Je    GN3
    Stosb                ;Store the character in name buffer
    Lodsb
    Jmp    GN2            ;Back for more characters
GN3:    Mov    DI,Offset OutName    ;Point to 2nd name
GN4:    Lodsb                ;Get next character
    Cmp    AL,' '            ;Skip any leading spaces
    Je    GN4
GN5:    Cmp    AL,CR            ;End of command tail
    Je    GN6
    Cmp    AL,' '
    Je    GN6
    Stosb
    Lodsb
    Jmp    GN5
GN6:    Ret

GNErr:    Mov    DX,Offset BHErr
    Call    PText
    Pop    AX            ;Clean up the stack
    Mov    AX,4C01H        ;Set error code & terminate process
    Int    21H
GetNames    endp

%OUT    -    LoadTxt
LoadTxt    proc near
    Mov    DX,Offset InName    ;Point to file name
    Mov    AL,0            ;read access
    Mov    AH,3dH            ;Open the file
    Int    21H
    Jc    LTErr            ;If we get an error, report it
    Mov    Handle,AX        ;Store the returned handle
    Mov    BX,AX            ;File handle for read file
    Mov    DX,Offset SepChar    ;Address of file buffer start
    Mov    CX,MaxSize        ;Calculate max number of bytes to read
    Sub    CX,EndPgm        ;allowing 128 bytes for .COM pgm stack
    Mov    MaxBytes,CX        ;Save the requested number of bytes
    Mov    AH,3FH            ;Read file/device function
    Int    21H
    Jc    LTErr            ;Report any error
    Cmp    AX,MaxBytes        ;Same read as asked for?
    Je    LTLenErr        ;Almost certainly, file too long
    Mov    BytesRead,AX        ;Store number of bytes read in
    Mov    BX,Handle        ;Close file
    Mov    AH,3EH            ;Close file function
    Int    21H
    Ret
LTErr:    Mov    DX,Offset LoadErr    ;Print error message
    Call    PText
    Pop    AX            ;Clean up the stack
    Mov    AX,4C01H        ;Set error code & terminate process
    Int    21H
LTLenErr:
    Mov    DX,Offset LenErr    ;Print error message - file too long
    Call    PText
    Pop    AX            ;Clean up the stack
    Mov    AX,4C01H        ;Set error code & terminate process
    Int    21H
LoadTxt    endp

%OUT    -    SaveFile
SaveFile    proc near
    Mov    Current,Offset Buffer + 11 ;Store pointer to first screen
    Mov    DI,Offset Buffer + 9    ;Initialize pointer for cmd address
    Mov    SI,Offset Buffer    ;Point to start of text
SF1:    Lodsb                ;Main loop for commands starts here
    Cmp    AL,SepChar        ;End of help text file?
    Je    SF6
    Mov    CX,9
SF2:    Lodsb
    Cmp    AL,CR            ;End of a command?
    Je    SF3
    Loop    SF2
    Jmp    SFCErr            ;We fell out of loop = error
SF3:    Cmp    CX,1            ;We should have been on last iteration
    Jne    SFCErr            ;If not, error in command length
    Mov    DI,SI            ;Point DI to storage for next cmd addr
    Dec    DI
SF4:    Lodsb                ;Look for end of prompt string
    Cmp    AL,CR            ;End of help text?
    Jne    SF4
    Mov    byte ptr [SI-1],0    ;Terminate prompt with 0 byte
SF5:    Lodsb
    Cmp    AL,SepChar        ;Look for end of help text
    Jne    SF5
    Mov    byte ptr [SI-1],0    ;Terminate text with 0 byte
    Cmp    byte ptr [SI],CR    ;Should be a CR, error if not
    Jne    SFTErr
    Add    SI,2            ;Skip past CRLF following SepChar
    Mov    [DI],SI            ;SI points to next command, store it
    Jmp    SF1            ;Keep indexing help text
SF6:    Mov    word ptr [DI],0        ;Signify the end of the help text
    Mov    byte ptr [SI-1],0    ;Terminate the text with 0 byte
    Mov    LastOfs,SI        ;Store end of memory used

; Now we have indexed the help text, write it plus the "engine" to disk

    Mov    DX,Offset OutName    ;Open output file
    Mov    CX,0            ;Normal file attribute
    Mov    AH,3CH            ;Create file function
    Int    21H
    Jnc    SF7
    Mov    DX,Offset SFErr1    ;Report any error
    Jmp    SFErr            ;In case of error
SF7:    Mov    Handle,AX        ;Store handle
    Mov    BX,AX            ;Handle for write
    Mov    DX,100H            ;Write whole pgm to disk file
    Mov    CX,LastOfs        ;Last memory location used
    Sub    CX,DX            ;Allow for PSP in byte count
    Mov    AH,40H            ;Write file function
    Int    21H
    Jnc    SF8
    Mov    DX,Offset SFErr2    ;Report any error
    Jmp    SFErr
SF8:    Mov    BX,Handle        ;Close file
    Mov    AH,3EH            ;Close file function
    Int    21H
    Ret
SFErr:    Call    PText
    Pop    AX            ;Clean up the stack
    Mov    AX,4C01H        ;Set error code & terminate
    Int    21H

SFCErr:    Mov    byte ptr [SI],0        ;Terminate text with 0 byte
    Push    DI            ;Save the pointer to start of command
    Mov    DX,Offset HCErr        ;Print 'Error in command ... '
    Call    PText
    Pop    DI
    Mov    DX,[DI]            ;Get address to bad area
    Call    PText
    Mov    AX,4C01H        ;Set error code & terminate
    Int    21H

SFTErr:    Push    SI            ;Save pointer to byte following error
    Mov    DX,Offset HTErr        ;Print 'Error in text ... '
    Call    PText
    Pop    SI            ;Recover pointer to bad byte
    Mov    Byte ptr [SI+60],0    ;Limit text display to one line
    Mov    DX,SI            ;Get address to bad area
    Call    PText
    Mov    AX,4C01H        ;Set error code & terminate
    Int    21H
SaveFile    endp

%OUT    -    Variables
Eight    Db    8
BadDos    Db 'HBUILD needs DOS version 2.0 or greater',CR,LF,0
BHMsg    Db 'Building Help Program',CR,LF,LF,0
BHErr    Db 'USAGE:',CR,LF,9
    DB 'HBUILD * [D:][Path]HelpFile.Ext [D:][Path]OutFile.COM',CR,LF,0
BHDone    Db 'Build Help successfully completed',CR,LF,0
LoadErr    Db 'Error: Cannot read input file',CR,LF,0
LenErr    Db 'Error: Help file too long to use',CR,LF,0
SFErr1    Db 'Error: Cannot open output file',CR,LF,0
SFErr2    Db 'Error: Cannot close output file',CR,LF,0
HTErr    Db 'Error: Misplaced separation character prior to -->',CR,LF,0
HCErr    Db 'Error: Help command not 9 characters long --> ',0

InName    Db    64 Dup(0)
OutName    Db    64 Dup(0)
ScrnAdd    Dw    0B800H            ;Default of color graphics screen
ScrnPos    DW    0            ;Position in screen buffer
Handle    Dw    0
BytesRead    Dw    0        ;Number of bytes read from help text
MaxBytes    Dw    0        ;Maximum number of bytes in Buffer
LastOfs        Dw    0        ;Last offset used by help text
Current        Dw    Offset Null    ;Current help screen address
CmdBuff    Db    9            ;User input command buffer
CmdLen    Db    0            ; as per DOS function 0AH layout
Cmd    Db    9 Dup(0)
Null    Db    '\70 PRESS RETURN \07',0,0
Author    Db    'HELP BUILD Version 1.6 - 16 December 1985',CR,LF
    Db    'Copyright (C) 1985 by David Gwillim ',CR,LF,0
HelpTxt    Dw    Offset Buffer
EndPgm    Dw    $

SepChar    Db    0            ;Separation character for help file
    Db    2 Dup(0)        ;Space for CRLF following SepChar
ExitChr    Db    0            ;Exit character
    Db    2 Dup(0)        ;Space for CRLF following ExitChr
Buffer    Db    0            ;Start of help text proper
Cseg    Ends
    End    Start