C Program to Convert Binary Number to Decimal Number System

• Write a C program to convert binary number to decimal number system.
• Wap in C to convert a base 2 number to a base 10 number.

Required Knowledge

• C printf and scanf functions
• While loop in C

This program converts a binary number( base 2) to decimal number (base 10). Binary number system is a base 2 number system using digits 0 and 1 whereas Decimal number system is base 10 and using digits from 0 to 9. Given a binary number as input from user convert it to decimal number.

For Example

00000111 in Binary is equivalent to 7 in Decimal number system.

Algorithm to convert Binary to Decimal number

• We multiply each binary digit with 2ⁱ and add them, where i is the position of the binary digit(starting from 0) from right side. Least significant digit is at position 0.
  Let’s convert 0101 binary number to decimal number
  Decimal number = 0*2³ + 1*2² + 0*2¹ + 1*2⁰ = 0 + 4 + 0 + 1 = 5

C program to convert a decimal number to octal number

#include <stdio.h>  
#include <math.h>    
   
int main() {  
    long binaryNumber, decimalNumber=0;  
    int position=0, digit;  
   
    printf("Enter a Binary Number\n");  
    scanf("%ld", &binaryNumber);  
     
    while(binaryNumber!=0) {   
        /* get the least significant digit of binary number */
 
        digit = binaryNumber%10;
        decimalNumber += digit*pow(2, position);    
   
        position++;  
        binaryNumber /= 10;  
    }  
  
    printf("Decimal Number : %ld", decimalNumber);  
   
    return 0;  
}

Program Output

Enter a Binary Number
00000111
Decimal Number : 7

Enter a Binary Number
00010000
Decimal Number : 16