Binary Addition

/*
 * Enter two numbers in base 10, convert them in binary
 * and find their sum
 */
import java.io.*;
class BinarySum

{
public static void main(String args[])throws IOException
{
    int m,n,u,v,x,y,z,p,r,i,d,e;

    BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
    System.out.print("Enter the first number (base 10): ");
        m= Integer.parseInt(br.readLine());
    System.out.print("Enter the second number (base 10): ");
        n= Integer.parseInt(br.readLine());

    //Arrays to store numbers in binary form
    int a[]= new int [20];
    int b[]=new int [20];

    //Array to store the sum of binary numbers
    int c[]= new int[50];

    p=m;
    x=0;
    //Convert the number to binary and store in an array
    while(p>0)
    {
        a[x++]=p%2;
        p=p/2;
    }

    System.out.print(m+"=");
        for(i=x-1;i>=0;i--)
        {
            System.out.print(a[i]);
        }
    System.out.println();

    p=n;
    y=0;
    //Convert the number to binary and store in an array
    while(p>0)
    {
        b[y++]=p%2;
        p=p/2;
    }
    System.out.print(n+"=");
        for(i=y-1;i>=0;i--)
        {
            System.out.print(b[i]);
        }
    e=z=u=v=0;

    /*
    * To understand the following logic, you need to know binary addition.
    * In binary addition:
    *  0 + 0 = 0
    *  0 + 1 = 1
    *  1 + 0 = 1
    *  1 + 1 = 10 (read as 0 CARRY 1)
    *  1 + 1 + 1 = 11 ( read as 1 CARRY 1)
    */

    do{

        d=a[u]+b[v]+e; //Add the digits
        if(d==2){   
            c[z++]=0;
            e=1;
        }
        else if(d==3){
            c[z++]=1;
            e=1;
        }
        else{
            c[z++]=d;
            e=0;
        }
        u++;
        v++;
    }while(u < x && v < y);

    //If any digit is left in the first array copy them 
    // into the sum array after adding the carry

    if(u < x){
        while(u < x){
        d=a[u++]+e;
            if(d==2){
                c[z++]=0;
                e=1;
            }
            else if(d==3){
            c[z++]=1;
            e=1;
            }
            else{
            c[z++]=d;
            e=0;
            }
        }
    }
    //If any digit is left in the second array copy them 
    // into the sum array after adding the carry
    else if(v < y){
        while(v < y){
        d=b[v++]+e;
            if(d==2){
                c[z++]=0;
                e=1;
            }
            else if(d==3){
            c[z++]=1;
            e=1;
            }
            else{
            c[z++]=d;
            e=0;
            }
        }
    }
    //If a carry is still left copy it at the last in the sum array
    if(e==1){
        c[z++]=e;
    }

System.out.print("\nSum of the two binary numbers : ");
    for(i=z-1;i>=0;i--)
    System.out.print(c[i]);

}//end of main
}//end of class