Tandy 1000 Programmer's Reference Guide

Chapter 1 I System Calls
Function Request
Interrupt 21H
See “Function Calls” later in this chapter for a description of the
MS-DOS system functions.
Entry Conditions:
AH = function call number
Other registers as specified in individual function.
Exit Conditions:
As specified in individual function.
Example:
To call the Get Time function:
mov ah,ECH ;Get Time 15 Function 2CH
int 21 H ;THIS INTERRUPT
14

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