C program to convert binary to decimal

To convert a binary number to decimal in a C program, you can use a simple algorithm that iterates through each digit of the binary number and accumulates the decimal value. Here's a detailed C program to convert a binary number to decimal with an example and output:

#include <stdio.h>
#include <math.h>

// Function to convert a binary number to decimal
int binaryToDecimal(long long binary) {
    int decimal = 0, i = 0, remainder;
    
    while (binary != 0) {
        remainder = binary % 10;
        binary /= 10;
        decimal += remainder * pow(2, i);
        ++i;
    }
    
    return decimal;
}

int main() {
    long long binary;
    
    // Input binary number
    printf("Enter a binary number: ");
    scanf("%lld", &binary);
    
    // Check if the input is a binary number
    long long temp = binary;
    int isBinary = 1;
    while (temp != 0) {
        int digit = temp % 10;
        if (digit != 0 && digit != 1) {
            isBinary = 0;
            break;
        }
        temp /= 10;
    }
    
    if (isBinary) {
        int decimal = binaryToDecimal(binary);
        printf("Decimal equivalent: %d\n", decimal);
    } else {
        printf("Invalid input. Please enter a binary number (0s and 1s only).\n");
    }

    return 0;
}
 

Explanation:

1. We include the necessary header files, stdio.h for input/output functions and math.h for the power function pow().

2. We define a function binaryToDecimal that takes a binary number as input and converts it to a decimal number using a while loop.

3. In the main function:

   • We ask the user to input a binary number.
   • We check whether the input is a valid binary number by iterating through each digit and ensuring that it contains only 0s and 1s.
   • If the input is a valid binary number, we call the binaryToDecimal function to convert it and then display the result as the decimal equivalent.

Example and Output:

Enter a binary number: 1010
Decimal equivalent: 10 

In this example, the user entered the binary number 1010, and the program correctly converted it to the decimal equivalent, which is 10.