need a

in C that converts any given BCD to GRAY Code, and any given GRAY to BCD. I am a started so little halp ;)

/*
      Convert decimal number to Grey code and back again
    */
     
    # include<stdio.h>
     
    #define SIZE 32
     
    int bits[SIZE], i; // could be chars in 8 bit machine
    unsigned long num; // could be int if less than 17 bit Grey code
     
    void main(){
    printf("\n ");
    printf("%d",SIZE);
    printf(" bit number conversion\n");
     
    printf("\n Enter number ");
    scanf("%lu",&num);
     
    /* converting number to binary equivalent */
    /* MSB is 1st element in array */
    for(i = 0; i < SIZE; i ++){
    bits[SIZE-1-i] = (num >> i) & 1;
    }
     
    /* printing binary */
    printf(" Binary ");
    for(i = 0; i < SIZE; i ++){
    printf("%d",bits[i]);
    }
     
    /* in-line gray code conversion */
    for(i = SIZE-1; i > 0; i --){
    bits[i] = bits[i] ^ bits[i - 1];
    }
     
    /* printing gray code */
    printf("\n Gray code ");
    for(i = 0; i < SIZE; i ++){
    printf("%d",bits[i]);
    }
     
    /* in-line conversion back to binary */
    for(i = 1; i < SIZE; i++){
    bits[i] = bits[i] ^ bits[i - 1];
    }
     
    /* reprinting binary */
    printf("\n Restored binary ");
    for(i=0;i<SIZE;i++){
    printf("%d",bits[i]);
    }
     
    /* convert back to decimal */
    num = 0;
    for (i = 0; i < SIZE; i ++){
    num = (num<<1) | bits[i];
    }
     
    /* reprinting decimal number */
    printf("\n Restored decimal ");
    printf("%lu",num);
    printf("\n");
    }

Reference: http://www.daniweb.com/software-development/c/code/216355

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