dec2bin

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

/*
 * maximum bit size
 * for different
 * sizes of numbers
 */
#define MAX_BITS 32

/*
 * check to see if the
 * given bit is set (1)
 * or not (0)
 */
int is_bit (int i) {
    return i & 0x01;
}

/*
 * bit shift each bit
 * in number and check
 * if bit is set (1) or
 * not (0) and put into
 * array
 */
void dec_to_bin (int n, char *buf) {
    int i;
    for (i = 0; i < MAX_BITS; i++) {
        buf[MAX_BITS-i-1] = (is_bit (n >> i)) ? '1' : '0';
    }
}

/*
 * print bits with
 * iteration
 */
int print_bits (const char *buf) {
    int i;
    for (i = 0; i < MAX_BITS; i++) {
        if (i != 0 && i % 8 == 0) {
            putchar (' ');
        }
        putchar (buf[i]);
    }
    putchar ('\n');

    return i;
}

int main (int argc, char *argv[]) {
    char buf[MAX_BITS];
    memset (buf, '0', MAX_BITS);

    dec_to_bin (atoi (argv[1]), buf);

    printf ("%d to bits: ", atoi (argv[1]));

    print_bits (buf);

    return 0;
}