This API controls the truncation and concatenation of print streams for
network printers. ┌───────────────┬──────────────────────────────────────────────────────────────┐
│ ON │ REGISTER │
│ ENTRY │ CONTENTS │
├───────────────┼──────────────────────────────────────────────────────────────┤
│ AH │ 06 │
├───────────────┼──────────────────────────────────────────────────────────────┤
│ AL │ 01 ; Set print output into │
│ │ Concatenation mode │
│ │ 02 ; Set print output into │
│ │ Truncation mode │
│ │ 03 ; Truncate print stream │
└───────────────┴──────────────────────────────────────────────────────────────┘
┌───────────────┬──────────────────────────────────────────────────────────────┐
│ ON │ REGISTER │
│ RETURN │ CONTENTS │
├───────────────┼──────────────────────────────────────────────────────────────┤
│ AX │ DOS error code if carry set │
│ │ None if carry flag not set │
└───────────────┴──────────────────────────────────────────────────────────────┘
Remarks
DOS defines separate print streams for each of up to nine redirected printers. These printers are LPT1 (or PRN)-LPT9.
Note: PC LAN Program had only one print stream for each redirected print device. DLS has one interrupt 17H print stream for each redirected print device and multiple interrupt 21H print streams for each redirected print device.
Interrupt 17H print streams are delimited by the following events:
DOS interrupt 21H printing is delimited by the following events:
DOS normally is in Truncation mode, which means the interrupt 17H print stream delimiters previously listed take effect. Concatenation mode (AL=01) causes DOS to ignore the interrupt 17H stream delimiters. In this mode, the interrupt 17H print stream is delimited only when a single DOS command ends or when a DOS batch (.BAT) process ends. This allows output from several commands to be kept together if the commands are in a batch file. Set Concatenation mode changes the stream state for all redirected printers. It has no effect on nonredirected printers or file handle printing.
Set Truncation mode (AL=02) returns DOS to Truncation mode. It is used to cancel the Set Concatenation mode function. This call does not truncate streams; the next stream delimiter causes the truncation. Truncation mode is set automatically at the end of all DOS batch files and at the end of any command not in a batch file. Set Truncation mode changes the stream state for all redirected printers. It has no effect on nonredirected printers.
Not all programs print output in such a way that DOS can determine when a print stream ends. This situation occurs most often when interrupt 17H is used for printing. Truncate Print Stream (AL=03) allows a program to indicate that the data currently printed is a complete stream and should be ended and printed.
This function serves the same purpose as the Ctrl+Alt+* (on the numeric keypad) key sequence that is available to users to end print streams. Truncate Print Stream truncates all interrupt 17H print streams. It has no affect on nonredirected printers or file handle printing. The DLS program must be started for this function call to work.