C++ int to binary string function code

C++ int to binary string conversion program simple example with code documentation. This is custom function implementation example to convert int to binary string in C++. However, we can also use  itoa c++ library function for the conversion .

We will consider unsigned long, so, we can convert int to binary string from 0 to 4,294,967,295 number as this is the unsigned long range.

Below is the C++ code to convert int to binary string in C++ with code comments.

C++ int to binary string conversion code


/*--------------------------------------------------
* C++ - Int to Binary String Conversion function
*/

#include <iostream>
using namespace std;

string intToBinaryString( unsigned long n )
{

      /*
      * Create char array of size = 32+1
      * (1 for null terminated string) =33 to
      * accommodate 32 byte chars as unsigned long range
      *  0 to 4,294,967,295 can be accommodated int to it
      * 
      * Size of unsigned long is 4 bytes, hence for
      * 32 byte char array, we need to multiply by 8
      */     

      char     bArray[ (sizeof( unsigned long ) * 8) + 1 ];

      //index = 32 to fetch each 32 slots
      unsigned index  = sizeof( unsigned long ) * 8;

      char temp =0;
      bArray[ index ] = '\0';

      do{          

            //bArary[ --index ] = '0' + (n & 1);

            //Breaking above line to understand better.
            temp = (n & 1); // Finding 0 or 1 in LSB
            // Adding ASCII 0 to convert Binary to ASCII
            temp = temp + '0';

            // Copying final ASCII equivalent BIT value (0 or 1)
            bArray[ --index ] = temp;

            //In while expression :n >>= 1 or equivalent to it is n =n>>1
            //can be used. Shifting the Value to RIGHT by one
            //to check the NEXT LSB bit.
            //Exits when n becomes ZERO.

      }while (n >>= 1);

      //bArray contains base address. So, jump to
      //base address + current index to fetch
      //the binary representation.


      return string( bArray + index );
}


/*---------------------------------------
* Test - int to binary string C++
*/
int main(){

      int n;
      cout<<"Enter int number: "<<endl;
      cin>> n;

      std::string bString = intToBinaryString(n);

      cout<<"Binary of "<< n << " is " << bString.c_str()<<endl;

      return 0;

}

Output:
Enter int number:
7
Binary of 7 is 111

Enter int number:
24
Binary of 24 is 11000

Enter int number:
512
Binary of 512 is 1000000000

C++ int to binary string function code

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