Compaq Deskpro EP 6233 Technical Reference Manual page 192

Appendix C Keyboard
C.2.3.2 Multi-Keystroke Functions
Shift - The Shift key (pos. 75/86), when held down, produces a shift state (upper case) for keys
in positions 17-29, 30, 39-51, 60-70, and 76-85 as long as the Caps Lock key (pos. 59) is
toggled off. If the Caps Lock key is toggled on, then a held Shift key produces the lower
(normal) case for the identified pressed keys. The Shift key also reverses the Num Lock state of
key positions 55-57, 72, 74, 88-90, 100, and 101.
Ctrl - The Ctrl keys (pos. 92/96) can be used in conjunction with keys in positions 1-13, 16, 17-
34, 39-54, 60-71, and 76-84. The application determines the actual function. Both Ctrl key
positions provide identical functionality. The pressed combination of Ctrl and Break (pos. 16)
results in the generation of BIOS function INT 1Bh. This software interrupt provides a method of
exiting an application and generally halts execution of the current program.
Alt - The Alt keys (pos. 93/95) can be used in conjunction with the same keys available for use
with the Ctrl keys with the exception that position 14 (SysRq) is available instead of position
16 (Break). The Alt key can also be used in conjunction with the numeric keypad keys (pos. 55-
57, 72-74, and 88-90) to enter the decimal value of an ASCII character code from 1-255. The
application determines the actual function of the keystrokes. Both Alt key positions provide
identical functionality.
The combination keystroke of Alt and SysRq results in software interrupt 15h, AX=8500h
being executed. It is up to the application to use or not use this BIOS function.
The Ctrl and Alt keys can be used together in conjunction with keys in positions 1-13, 17-34, 39-
54, 60-71, and 76-84. The Ctrl and Alt key positions used and the sequence in which they are
pressed make no difference as long as they are held down at the time the third key is pressed. The
Ctrl, Alt, and Delete keystroke combination (required twice if in the Windows environment)
initiates a system reset (warm boot) that is handled by the BIOS.
C-8 Compaq Personal Computers
Changed - March 1998