detect.c

_计算实用教程Visual C++6.0实用教程

/*detect.c*/
/*This piece of code determines if the PC has any parallel adapter*/
/*If yes, it finds out and prints the addresses of the DATA, CONTROL */
/*and the STATUS ports*/

#include <stdio.h>
#include <dos.h>
#include <conio.h>
#include <process.h>


main()
{
int dport, cport, sport, select, offset;

clrscr(); /*clear screen*/

printf("\tProgram to detect the parallel printer adapter.\n");
printf("Enter 1, 2 or 3 to detect LPT1, LPT2 or LPT3 respectively.\n\n");

/*wait for a keystroke*/
select=getch();

/*loop indefinitely if the key pressed is not `1', `2' or `3'*/
while ( (select != '1') && (select != '2') && (select != '3') )
{ printf("Invalid number. Enter 1, 2 or 3\n");
select=getch();
}


if(select == '1') offset = 0x08;
if (select == '2') offset = 0x0a;
if (select == '3') offset = 0x0c;

/*now look into BIOS area to determine the address of the particular*/
/*parallel adapter*/
dport=peek(0x40, offset);

/*If the address is zero, means that particular parallel adapter*/
/*is not present. No point in continuing. Abort the code here*/
if (dport ==0) 
{printf("Sorry, On this machine LPT%d does not exist\n", select-'0'); 
exit(0);}

/*else print the port addresses of the DATA, STATUS and CONTROL ports*/
printf("\nLPT%d detected!\n", select -'0');
printf("DATA port is %x\n", dport);
printf("STATUS port is %x\n", dport+1);
printf("CONTROL port is %x\n", dport+2);

return 1;

}