char a;
char i;


void main ()
{

for (i=0; i<=3; i++)
    {
    PORTC.i = 0;
    PORTB.i = 0;
    test_lines;
    }
}


void test_lines ()

{
for (a=4; a<=7; a++)
    {
    if PORTC.a=1 PORTB.a=debounce(a)
    }
}

void debounce (char a)

{
delay(5);
if PORTC.a=1 return 1;
return 0;
}

void delay(char millisec)
/* delays a multiple of 1 millisecond at 4 MHz */
{
OPTION = 2; /* prescaler divide by 8 */
do {
TMR0 = 0;
clrwdt(); /* only if necessary */
while (TMR0 < 125) /* 125 * 8 = 1000 */
;
} while (-- millisec > 0);
}