C++ Program to Convert Decimal Number to Binary

In a computer system, the binary number is expressed in the binary numeral system while the decimal number is in the decimal numeral system. The binary number is in base 2 while the decimal number is in base 10. Examples of decimal numbers and their corresponding binary numbers are as follows −

A program that converts the decimal numbers into binary is as follows −

Example

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#include <iostream>
using namespace std;
void DecimalToBinary(int n) {
   int binaryNumber[100], num=n;
   int i = 0;
   while (n > 0) {
      binaryNumber[i] = n % 2;
      n = n / 2;
      i++;
   }
   cout<<"Binary form of "<<num<<" is ";
   for (int j = i - 1; j >= 0; j--)
   cout << binaryNumber[j];
   cout<<endl;
}
int main() {
   DecimalToBinary(15);
   DecimalToBinary(10);
   DecimalToBinary(18);
   DecimalToBinary(27);
   return 0;
}

Output

Binary form of 15 is 1111
Binary form of 10 is 1010
Binary form of 18 is 10010
Binary form of 27 is 11011

In the above program, the DecimalToBinary function has binary value of the decimal number n and is stored in the array binaryNumber[]. A while loop is used and the result of the n modulus 2 operation is stored in binaryNumber[] for each iteration of the loop.

This is shown using the following code snippet.

while (n > 0) {
   binaryNumber[i] = n % 2;
   n = n / 2;
   i++;
}

After this, the binary number is displayed using a for loop. This is shown as follows −

cout<<"Binary form of "<<num<<" is ";
for (int j = i - 1; j >= 0; j--)
cout << binaryNumber[j];

The main() function contains only the function calls to DecimalToBinary() for various decimal numbers.

This is shown in the following code snippet.

DecimalToBinary(15);
DecimalToBinary(10);
DecimalToBinary(18);
DecimalToBinary(27);