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Q66744: How to POKE Keystrokes Such as F3 (Last Command) into Keyboard

Article: Q66744
Product(s): See article
Version(s): 3.00 4.00 4.00b 4.50
Operating System(s): MS-DOS
Keyword(s): ENDUSER | B_BasicCom | mspl13_basic
Last Modified: 8-NOV-1990

Instead of using CALL INTERRUPT to push keystrokes into the keyboard
buffer, the code example below POKEs a key directly into the keyboard
buffer area in memory under MS-DOS.

This information applies to QuickBASIC versions 3.00, 4.00, 4.00b, and
4.50 for MS-DOS; to Microsoft BASIC Compiler versions 6.00 and 6.00b
for MS-DOS; and to Microsoft BASIC Professional Development System
(PDS) versions 7.00 and 7.10 for MS-DOS.

In many applications, it is often useful to echo the command line to
the screen during repetitive execution of a program. This makes the
program easier to use by allowing you to avoid typing in the command
line at the completion of each instance of the program. The code
example below shows a quick way to push the F3 keystroke into the
keyboard buffer, which echoes the previously entered command line to
the screen.

Code Example
------------

DEF SEG = 0      ' Set default segment to 0
POKE 1054,0      ' Push 0 for extended key into keyboard buffer
POKE 1055, 61    ' Push F3 key scan code into keyboard buffer
POKE 1050, 30    ' Set beginning (head) buffer position
POKE 0152, 32    ' Set ending (tail) buffer position
DEF SEG          ' Return current segment pointer to default segment

References
----------

For more articles about reading from and writing to the keyboard
buffer, search in this Knowledge Base for the following words:

   interrupt and keyboard and buffer

The addresses for the keyboard buffer area, head, and tail (used in
the above code example) are documented in "The New Peter Norton
Programmer's Guide to the IBM PC & PS/2" by Peter Norton and Richard
Wilton, published by Microsoft Press (1988).

Keyboard scan codes are documented in Appendix D of "Microsoft
QuickBASIC 4.5: Programming in BASIC"; in Appendix A of "Microsoft
QuickBASIC 4.0: Language Reference" for 4.00 and 4.00b; in Appendix A
of "Microsoft BASIC Compiler 6.0: Language Reference" for 6.00 and
6.00b; and in Appendix A of "Microsoft BASIC 7.0: Language Reference"
manual for BASIC PDS versions 7.00 and 7.10.

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