Tandy 1000 Programmer's Reference Guide

Chapter 1 I System Calls
Move a File Pointer Function Call 42H
Moves the readlwrite pointer a specified number of bytes accord-
ing
to the following methods:
0 - The pointer is moved to the specified offset from
1 - The pointer is moved to the current location plus
2
- The pointer is moved to the end of file plus the
the beginning of the file.
the offset.
offset.
Entry Conditions:
AH = 42H
CX:DX
= distance to move the pointer, offset in bytes (CX
contains the most significant part)
AL = method of moving (0, 1, or 2; see above)
BX = file handle
Exit Conditions:
Carry set:
Carry not set:
Error Returns:
AX = 6
AX = error code
DX:AX = new file pointer position
Invalid handle. The handle passed in BX is not cur-
rently open.
Invalid function. The function passed in AL was not
in the range
0-2.
AX = 1
Example:
LSeek eq" 42H
mov dx,offsetlow
mov cx,offsethigh
mov a1 ,method
mQV bx ,handle
mQv ah,LSeek
Int
21 H
114

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