Q68944: Output to stdprn Is in Binary (Untranslated) Mode

Article: Q68944
Product(s): See article
Version(s): 3.x 4.x 5.x 6.00a 6.00 | 5.10 6.00 6.00a
Operating System(s): MS-DOS | OS/2
Keyword(s): ENDUSER | | mspl13_c
Last Modified: 6-FEB-1991

The C start-up code automatically opens five files for a program's
use. The "stdprn" file (PRN device) is opened in binary mode, which is
important to remember when printing to printers that require a
carriage return/line feed combination to end a line (for example, some
laser printers). In those cases, you do one of the following:

1. Change your output routines to send a CR/LF pair (\n\r).

2. Reopen stdprn in text mode so that the translation is handled by
   the run-time library.

3. Change the mode of the file to O_TEXT. You must remember to flush
   the buffer before doing this.

The following is a code fragment that illustrates each method:

#include <stdio.h>
#include <io.h>
#include <fcntl.h>

void main(void)
{
   FILE *txtprn;

   fprintf(stdprn, "untranslated\n");        // Standard mode

   fprintf(stdprn, "CRLF pair added \n\r");  // Method 1

   txtprn=freopen("PRN", "wt",stdprn);       // Method 2

   fprintf(txtprn, "translated\n");

   fflush(stdprn);                           // Flush the buffer first

   setmode(fileno(stdprn), O_TEXT);          // Method 3

   fprintf(stdprn, "translated\n");
}

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