Tandy 600 Programmer's Reference Manual page 18

FUNCTION
01
h
-
Read
Keyboard and Echo
AX
BX
CX
DX
SP:
BP:
SI:
Dl:
IP:
FLG
CS
DS
SS
ES
XXXXXXXX
xxxxxxxx
Entry:
AH
=
01 h (function
code)
Exit
AX =
Character
Typed
Function 01 h waits
for
a character
to
be
typed
at
the keyboard, then
echos
the
character
to
the display
and
returns
it
in
AX.
13