Learning C Functions : _bios_printer ( Dos Only )

C Programming :
Function :_bios_printer

Syntax

#include <bios.h>
unsigned _bios_printer(int cmd, int port, int abyte);

Description

_bios_printer performs various printer functions on the printer identified by the parameter port using BIOS interrupt 0x17.
A port value of 0 corresponds to LPT1; a port value of 1 corresponds to LPT2; and so on.
The value of cmd can be one of the following values (defined in bios.h):

_PRINTER_WRITE    Prints the character in abyte. The value of abyte can be 0 to 255.
_PRINTER_INIT    Initializes the printer port. The abyte argument is ignored.
_PRINTER_STATUS    Reads the printer status. The abyte argument is ignored.

Return Value

The value returned from any of these operations is the current printer status, which is obtained by ORing these bit values together:

Bit 0    0x01    Device time out
Bit 3    0x08     I/O error
Bit 4    0x10     Selected
Bit 5    0x20     Out of paper
Bit 6    0x40     Acknowledge
Bit 7    0x80     Not busy

Example :
 
/* _bios_printer example */

#include <stdio.h>
#include <conio.h>
#include <bios.h>

int main(void)
{
   unsigned PortNum = 0x1;  /* LPT1 -> 0, LPT2 -> 1 */
  unsigned status, abyte = 0;
  printf("Please turn off your printer.\n\
        Press any key to continue\n");
  getch();
  status = _bios_printer(_PRINTER_STATUS, PortNum, abyte);
   if (status & 0x01)
      printf("Device time out.\n");
   if (status & 0x08)
      printf("I/O error.\n");
   if (status & 0x10)
      printf("Selected.\n");
   if (status & 0x20)
      printf("Out of paper.\n");
   if (status & 0x40)
      printf("Acknowledge.\n");
   if (status & 0x80)
      printf("Not busy.\n");
   return 0;
}