Tandy 1000 SL Technical Reference Manual page 525

Software
Scan Keyboard
Set up the zero flag (Z flag) to indicate whether a character is avail-
able to read from the keyboard or not. If a character is available, return
the ASCII value of the character and the keyboard scan code. The entry
remains in the keyboard buffer (non-destructive read).
Entry Conditions
AH
=
1
Exit Conditions
z
=
no character available
N Z
AL
AH
=
keyboard scan code
=
a character is available, in which case:
=
ASCII value o f character
Get Shift Status
Return the current shift status.
Entry Conditions
AH
=
2
Exit Conditions
AL
=
current shift status (bit settings: set
=
true, reset
=
false)
Bit 0
=
RIGHT SHIFT key depressed
Bit
1
=
LEFT SHIFT key depressed
Bit 2
=
CTRL (control) key depressed
Bit 3
=
ALT (alternate mode) key depressed
Bit 4
=
SCROLL state active
Bit 5
=
NUMBER lock engaged
Bit 6
=
CAPS lock engaged
Bit 7
=
INSERT state active
4.