Tandy 1000 Programmer's Reference Guide

Chapter 1 I System Calls
RBRead
Random Block Read Function Call 27H
Reads the specified number of records (calculated from the re-
cord size field
at offset 0EH of the FCB), starting at the record
specified by the relative record field (offset 21H). The records are
placed
at the Disk Transfer Address. The current block (offset
BCH), current record (offset 20H), and relative record (offset
21H) fields are set to address the next record.
If the number of records
to read is specified as zero, the call re-
turns without reading any records (no operation).
Entry Conditions:
AH = 27H
CX
= number of records to read
DS:DX = pointer to the opened FCB of the file to read
E xi t Conditions :
CX = actual number of records read
If AL
= 00H, all records were read successfully.
IfAL
= 01H, end of file was encountered before all records were
read; the last record is complete.
IfAL
= 02H, wrap-around above address FFFFH in the disk
transfer segment would occur if all records were read;
therefore, only as many records were read as was possi-
ble without wrap-around.
If AL
= 03H, end of file was encountered before all records were
read; the last record is partial.
Macro Definition:
ran-block-read macro fcb,count,rec_5ize
mov dx,offsetfcb
mov cx, coun t
mov wordptr fcb[l41,rec_5ize
mov ah,27H
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