#include <reg51.h>

char bdata dbit; // Bit addressing variable.

sbit x1 = dbit^0; // 0 dbit of dbit.
sbit x2 = dbit^1; // 1 dbit of dbit.
sbit y1 = dbit^2; // 2 dbit of dbit.
sbit y2 = dbit^3; // 3 dbit of dbit.

sbit z = P0^0; // 0 dbit of P0 port.

main( void ) {
    // Generate table of truth.
    P1 = 0;
    for( dbit = 0; dbit < 16; dbit++ ) {
        z = ( y1 | ~x1 ) & ( y2 & x2 | x1 );
        P1 <<= z;
    }
    while( 1 );
}