Tandy 600 Programmer's Reference Manual page 61

FUNCTION
D4h
-
Return
Size of Free
Memory
AX
BX
CX
DX
SP:
BP:
SI:
Dl:
IP:
FLG
CS
DS
SS
ES
XXXXXXXX
xxxxxxxx
Entry:
AH =
D4h
(function
code)
Exit
AX
=
Size of free
memory
Function
D4h
returns
the
total
number
of
paragraphs
of
free
memory
remaining
in
the
system
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