Tandy 1000 Programmer's Reference Guide

Chapter 1 I System Calls
Write to a File or Device
Function Call
40H
Transfers a specified number of bytes from a buffer into a file. If
the number of bytes written is not the same as the number re-
quested, then an error has occurred.
If the number of bytes
to be written is zero, the file size
is
set to the current position. Allocation units are allo-
cated
or released as required.
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 = 40H
DS:DX = pointer to buffer
CX = number of bytes to write
BX = file handle for file to write
Exit Conditions:
Carry set:
Carry not set:
Error Returns:
AX = 6
AX = error code
AX = number of bytes written
Invalid handle. The handle passed
rently open.
AX
= 5
in BX is not cur-
Access denied. The handle passed in BX was opened
in
a mode that did not allow writing.
Example:
Write equ 40H
Id5 dx,buffer
mov cx ,count
mov bx, handle
mov ah, Wr I te
int
21 H
112

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