Output to stdprn Is in Binary (Untranslated) Mode

MS-DOS                 | OS/2       | WINDOWS

The information in this article applies to:

• The C Run-time (CRT), included with:

      - Microsoft C for MS-DOS, versions 6.0, 6.0a, and 6.0ax
      - Microsoft C for OS/2, versions 6.0, and 6.0a
      - Microsoft C/C++ for MS-DOS, version 7.0
      - Microsoft Visual C++ for Windows, versions 1.0, 1.5, 1.51, and 1.52
  

SUMMARY

The 16-bit 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:

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

  -or-

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

  -or-

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

MORE INFORMATION

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");