Tandy 1000 Programmer's Reference Manual page 127

Chapter 1 I System Calls
SetBlock
Modify Allocated
Memory Blocks Function Call 4AH
Attempts to "grow" or "shrink" an allocated block of memory.
En try Conditions:
AH
=
4AH
ES
=
segment address of memory area
BX
=
requested memory area size, in paragraphs
Exit Conditions:
Carry set:
BX
=
maximum size possible, in paragraphs ( i f the
requested
size
was
not
available
on
a grow
request)
Carry not set:
No error.
Error Returns:
AX
=
9
Invalid block. The block specified in
ES
is not one
allocated via this call.
Arena trashed. The internal
consistency of the
memory arena has been destroyed. This is due to
a user program changing memory that does not
belong to it.
Not enough memory. There was not enough free
memory after the specified block to satisfy the
grow request.
AX
=
7
AX
=
8
Example:
S e t B l o c k
eq" 40H
mov
e 5 ,
b l o c k
mov
b x ,
n e w s i z e
mow
a h ,
S e t B l o c k
int 21 H
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