Tandy 1000 Programmer's Reference Guide

Chapter 1 I System Calls
Absolute Disk Read
Interrupt 25H
Transfers control to MS-DOS. The number of sectors speci-
fied in CX is read from the disk to the Disk Transfer
Address.
This call destroys all registers except the segment regis-
ters. Be sure
to save any registers your program uses be-
fore issuing the interrupt.
The system pushes the flags at the time
of the call; they
are still on the stack upon return. This is necessary be-
cause data is passed back in the current flags. Be sure
to pop the stack upon return to prevent uncontrolled
growth.
Entry Conditions:
AL = drive number (0 = A, 1 = B, etc.)
DS:BX = Disk Transfer Address
CX = number of sectors to read
DX = beginning relative sector
Exit Conditions:
Carry set:
Carry not set:
Error Returns:
Error codes are the same as for Interrupt 24H.
Macro Definition:
AL = error code
Operation was successful.
abs-di5k-read macro d~~k,buffer,num_sector~,f~rst_sector
mov a1,disk
mov bx,offset buffer
mov cx,num_sector5
mov dx,first_5ector
int 25H
endm
POPf
20

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