Decimal to binary conversion by C

We can convert decimal to binary using C program. In this article we will convert a decimal number to its equivalent binary number through a C program.

We know the base of decimal number is 10 and the base of binary number is 2. Here we will perform this program assuming that the size of integer is 4 byte (32 bits). We will use bitwise operator here to make this program. So, lets see the program to convert a decimal number to its equivalent binary number.

Decimal to binary using bitwise operator in C

#include <stdio.h>
int main(){
  int num, i, j;

  printf("Enter a decimal number to convert : ");
  scanf("%d", &num);

  printf("\nBinary equivalent of %d is = \n", num);

  for (i = 31; i >= 0; i--){
    j = num >> i;

    if (j & 1){


  return 0;

Output of this decimal to binary program:

decimal to binary program in c

Decimal to binary using array in C

//  we are updating

Output of this decimal to binary program

Convert decimal to binary using recursion

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

char *converter(int);

int main(){
  int num;
  char *a;

  printf("Enter a number to convert : ");
  scanf("%d", &num);

  a = converter(num);
  printf("\nBinary equivalent of %d is = %s\n", num, a);


  return 0;

char *converter(int k){
  int x, y, i;
  char *z;

  i = 0;
  z = (char*)malloc(32+1);

  if (z == NULL)

  for (x = 31 ; x >= 0 ; x--){
    y = k >> x;

    if (y & 1){
      *(z + i) = 1 + '0';
      *(z + i) = 0 + '0';
  *(z + i) = '\0';

  return  z;

Program output is as follows:

Enter a number to convert : 63

Binary equivalent of 63 is = 00000000000000000000000000111111

Process returned 0 (0x0)   execution time : 14.774 s
Press any key to continue.

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