Tandy 1000 Programmer's Reference Guide

Chapter 1 I System Calls
Read
Read from a
File
or Device Function Call 3FH
Transfers a specified number of bytes from a file into a buffer lo-
cation. It is not guaranteed that all bytes will be read. At most
1
line of text will be read from the keyboard. If the returned value
for number
of bytes read is zero, then the program tried to read
from the end of file.
All I/O is done using normalized pointers; no segment wrap-
around will occur. MS-DOS takes the pointer you specify in
DS:DX and modifies it
so that DX is OOOFH or smaller.
Entry Conditions:
AH = 3FH
DS:DX = pointer to buffer
CX = number of bytes to read
BX = file handle for the file to read
Exit Conditions:
Carry set:
Carry not set:
Error Returns:
AX = 6
AX = error code
AX = number of bytes read
Invalid handle. The handle passed in BX is not currently
open.
Access denied. The handle passed in BX was opened in
a
mode that did not allow reading.
AX = 5
Example:
Read equ 3FH
Ids dx, buff er
mov cx, coun t
mov bx,handIe
mov ah,Read
int 21 H
111

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