Tandy 1000 Programmer's Reference Guide

Chapter 1 I System Calls
RandomRead
Random Read Function Call 21H
Performs a random read of a record. The current block (offset
0CH) and current record (offset 20H) fields in the
FCB are set to
agree with the relative record field (offset 21H). The record ad-
dressed by these fields is then loaded
at the Disk Transfer
Address.
Entry Conditions:
AH = 21H
DS:DX
= pointer to the opened FCB of the file to read
Exit Conditions:
If AL =
IfAL =
If AL =
If AL =
Macro Definition:
read-ran macro fcb
00H, the read was completed successfully.
01H, end of file was encountered; no data is in the
record.
02H, there was not enough room at the Disk Transfer
Address
to read 1 record; the read was canceled.
03H, end of file was encountered; a partial record was
read and padded
to the record length with zeroes.
mQV dx,offsetfcb
mov ah,21H
Int 21 H
endm
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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