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

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

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