Tandy 1000 Programmer's Reference Guide

ChaQter 5 I Device Drivers
NON-DESTRUCTIVE READ NO WAIT
Commandcode = 5
ES:BX
13-BYTE Request Header
BYTE Read from device
If the character device returns busy bit
= 0 (characters in
buffer), then the next character that would be read is returned.
This character is not removed from the input buffer (hence the
term non-destructive read). This call allows
MS-DOS to look
ahead one input character.
STATUS
Command codes = 6 and 10
ES:BX
13-BYTE Request Header
All the driver must do is set the status word and the busy bit.
FLUSH
Command codes = 7 and 11
ES:BX
13-BYTE Request Header
The FLUSH call tells the driver
to flush (terminate) all pending
requests. This call is used
to flush the input queue on character
devices.
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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