#include <stdio.h>

/* 
 * full adder:  inputs A, B, Cin;  outputs Sum and Cout
 */
void FullAdder (int A, int B, int Cin, int *Sum, int *Cout)
{
    *Sum = (A ^ B) ^ Cin;
    *Cout = (A & B) | (A & Cin) | (B & Cin);
    return;
}

/*
 * 4-bit binary adder:  inputs A, B, Cin;  outputs Sum and Cout
 */
void FourBitAdder (int A[4], int B[4], int Cin, int Sum[4], int *Cout)
{
    int InternalCarry[5], i;
    InternalCarry[0]=Cin;
    for (i=0; i<=3; ++i)
	FullAdder (A[i], B[i], InternalCarry[i], &Sum[i], &InternalCarry[i+1]);
    *Cout=InternalCarry[4];
    return;
}

/*
 * test 4-bit adder for case 5 + 3, with Cin 0 or 1
 */
int main()
{
    int A[4] = {1, 0, 1, 0}, B[4]={1, 1, 0, 0}, Cin, Sum[4], Cout;
    for (Cin=0; Cin<=1; ++Cin) {
	FourBitAdder (A, B, Cin, Sum, &Cout);
	printf ("A=%d%d%d%d\tB=%d%d%d%d\tCin=%d\tSum=%d%d%d%d\tCout=%d\n",
		A[3], A[2], A[1], A[0], B[3], B[2], B[1], B[0], Cin,
		Sum[3], Sum[2], Sum[1], Sum[0], Cout);
    }
    return 0;
}