Tandy 1000 SL Technical Reference Manual page 526

BIOS Services
Store ASCII Character
Entry Conditions
AH
=
5
CL
=
ASCIIcharacter
CH
=
ScanCode
Exit Conditions
AL
=
00: Successful
AL
=
01: Buffer full
[C]
=
Operation failed
Extended Keyboard Read
Entry Conditions
AH
=
10H
Exit Conditions
AL
AH
=
keyboard scan code
=
ASCII value of Character
Extended ASCII Status
Entry Conditions
AH
=
11H
Exit Conditions
z
=
No character is available
NZ
AL
AH
=
keyboard scan code
=
A character is available, in which case:
=
ASCII value of character
5.