Tandy 1000 Programmer's Reference Guide

Chapter 1 I System Calls
DupZ
Force a Duplicate
of a File Handle
Function Call
46H
Takes a file handle that is already open and returns a new han-
dle that refers to the same file at the same position.
If there al-
ready
is a file open on the handle specified in CX, it is closed
first.
Entry Conditions:
AH = 46H
BX = existing file handle
CX = new file handle
Exit Conditions:
Carry set:
AX = error code
Carry not set:
No error.
Error Returns:
AX = 6
Invalid handle. The handle passed in BX is not currently
open.
Too many open files. There were no free handles available in
the current process
or the internal system tables were full.
AX = 4
Example:
Dup2 equ 46H
mov bx, handle
mov cx, newhandle
mov ah, Dupe
int 21 H
121

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