Category : Miscellaneous Language Source Code
Archive   : 21HELP.ZIP
Filename : 21HELP.DOC
Bob Kaye, 73047,2422
ARC file contains: 21H_HELP.COM - resident engine
21H0.TXT - menu and text file
21H1.TXT - text file
21H2.TXT - text file
21HELP.DOC - this file
DESCRIPTION
21HELP is sort of a poor man's Norton Guide describing each INT 21H function,
the other DOS interrupts and the ROM BIOS interrupts. There is a small
resident portion (2.2K), activated by
files from disk and displays the selected information. It is menu driven and
for each interrupt displays a description, the required register values to
call the function and the meaning of any register values returned by the
function or interrupt. There is also some cross referencing of functions.
The resident portion is kept small by using high video RAM for display
purposes; this does away with the need to copy the display of any underlying
program. An EGA card is required - though it should function with VGA also.
21HELP will adjust the display to any EGA text mode, but will not pop up
unless the display is set for 25 lines (generally, the default).
INSTALLATION
The resident portion of 21H_HELP has to know where the three text files are;
it will not search for them. There are two ways to provide this information:
when installing 21H_HELP, include the path on the command line or, using the
patch function, write the path to a copy of 21H_HELP on disk. After patching,
there is no longer a need to indicate the path on the command line.
Examples:
Not Patched - 21H_HELP [DRIVE] \PATH
21H_HELP C:\MISC
21H_HELP \TEXT\21H
Patched - 21H_HELP
In addition to the path, there are two command line parameters recognized by
21H_HELP - a patching parameter (-p or -P) and a parameter to un-install (-u
or -U). The hyphen ( - ) before the parameter is required.
When patching, a path must be included on the command line or an error message
will be displayed. A copy of 21H_HELP.COM must be in the current directory.
If 21H_HELP is the last TSR installed, the U parameter will un-install it and
free its allocated memory. If another resident program has been installed
after it, un-installation is not possible and an appropriate message will be
displayed.
Examples:
21H_HELP -u
21H_HELP -U
21H_HELP -p \MISC
21H_HELP -P C:\MISC\TXT
USE
Hitting
time its popped up, the main menu will be displayed with instructions at the
bottom of the screen. Thereafter, popping it up will display the last screen
displayed before exiting.
In most cases, the screen being displayed has instructions at the bottom. For
those that don't, hitting
to the underlying program. Hitting
CAVEATS
I haven't run into any compatibility problems, though my library of commercial
programs is limited. It seems to be compatible with all the TSRs I use,
though none of these are commercial, either. Since it does use VRAM pages
four and five, there is a potential problem with other programs that also use
this part of VRAM. A problem caused by this will result in a lost display in
the underlying program, but should not cause a crash. An orderly exit from
that program back to DOS should be possible.
DOS Critical Errors from within 21H_HELP are handled politely and should not
cause a crash or a hasty exit to the DOS prompt. A 'can't miss' error message
will be displayed and hitting any key will return you to the underlying
program. A Critical Error will be caused by 21H_HELP being unable to find the
text files where they're supposed to be or, if they're on a floppy, by the
door being open.
The indexing function of the resident code is keyed to the format of the three
text files as they were created. If the files get corrupted - or edited - the
chances are the display will not line up properly. They can be edited with a
word processor in the overwrite mode only, providing nothing is done to change
the size of the file. A blank line in the display does not mean 80 characters
can be inserted. The ASM file has some explanations regarding the indexing
scheme used by the menus to access specific data. If you feel the need to
change the text files, a file editor, rather than a word processor, is more
likely to maintain the integrity of the files.
Every effort was made to insure that the information displayed is correct.
Proofreading is not one of my strong points, so undoubtedly there are some
errors. If you find any serious contextual errors, please let me know so that
I can correct them and re-upload the text file. (Spelling errors I can live
with.)
The reserved (undocumented) functions described are those that I have picked
up from what various sources. I've used a number of them and they seem to
work - its your decision as to whether or not to use them in your own
programs.
Obviously, I'd like to know if there are any bugs...I've been using it for
several months with none arising. I'd also like any suggestions (I can think
of a few regarding the user interface.), criticisms and comments regarding its
utility.
CREDITS
Drew very heavily on Ray Duncan's Advanced MSDOS, Microsoft Press, 1986 for
a lot of the information.
Very nice! Thank you for this wonderful archive. I wonder why I found it only now. Long live the BBS file archives!
This is so awesome! 😀 I’d be cool if you could download an entire archive of this at once, though.
But one thing that puzzles me is the “mtswslnkmcjklsdlsbdmMICROSOFT” string. There is an article about it here. It is definitely worth a read: http://www.os2museum.com/wp/mtswslnk/