Tandy 1000 Programmer's Reference Guide

Chapter 1 I System Calls
Program Terminate
Interrupt 20H
Causes the current process to terminate and returns control to
its parent process. All open file handles are closed and the disk
buffer is written to disk. All files that have changed in length
should be closed before issuing this interrupt. (See Function
Calls 10H and 3EH
for descriptions of the Close File function
calls.)
The following exit addresses are restored from the Program Seg-
ment Prefix:
Exit Address Offset
Program Terminate
Critical Error
CONTROL-C
OAH
OEH
12H
Note: Interrupt 20H is provided for compatibility with earlier
versions
of MS-DOS. New programs should use Function Call
4CH, Terminate
a Process.
Entry Conditions:
CS = segment address of Program Segment Prefix
Macro Definition:
terminate macro
int
20H
endm
Example:
;CS must be equal to PSP values given at program start
;(ES and DS values)
INT 28H
;There 15 no return from this interrupt
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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