Tandy 1000 Programmer's Reference Guide

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 (if 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:
SetBlock eq” 40H
mov e5, block
mov bx, newsize
mow ah, SetBlock
int
21 H
125

Tandy 1000 Specifications

General

Processor	Intel 8088
Processor Speed	4.77 MHz
RAM	128 KB (expandable to 640 KB)
Operating System	MS-DOS 2.11
Manufacturer	Tandy Corporation
Release Year	1984
Storage	Single or double 5.25" floppy disk drive (360 KB), optional hard drive
Sound	Tandy 3-voice sound
Ports	Parallel, Serial
Graphics	CGA (Color Graphics Adapter)
Graphics Modes	320x200, 640x200