Interger to Bit String

Write a function to convert an integer into a bit string. For example, if input is 2, the output is "00000000000000000000000000000010" if the system is 32-bit, "0000000000000010" if the system is 16-bit and so on.

Strategy:
We will use bitwise manipulation and convert one bit at a time to character. We look at the right most bit and if it is a 0 bit, we add '0' character into our bit string. Otherwise, we add '1' character into our bit string.

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

#define BITS_PER_BYTE 8

char* int2bin(int num)
{
  int bitStrLen = sizeof(int) * BITS_PER_BYTE * sizeof(char)+1;

  char* p = (char*)malloc(bitStrLen);


  for (int i = (bitStrLen-1); i >= 0; i--)
  {
   if(i==bitStrLen-1)
      *(p+i)='\0';
   else
   {
    int k = 1 & num;
    *(p + i) = ((k == 1) ? '1' : '0');
    num >>= 1;}
  }
  return p;
}

int main()
{
  int num=156;
  size_t count=sizeof(int) * BITS_PER_BYTE * sizeof(char);
  char *str=(char*)malloc(count);
 
  memset (str,0,count);
  str=int2bin(num);

 printf(" The string format is %s\n",str);
  getchar();
  return 0;
}