Binary to Decimal Converter

A binary number is a sequence of bits (binary digits – 0’s and 1’s) of the form B_nB_n-1……B₁ B₀, where each B_i is a bit. The decimal equivalent is calculated by B_n * 2ⁿ+ B_n-1 * 2^n-1 + … + B₁ * 2 + B₀. Write a program to input a binary number and output the decimal equivalent. The sample input will not have more than 8 individual bits (i.e., the largest value to be entered is 11111111).

Example 1:

Enter binary number: 101
In decimal: 5

Example 2:

Enter binary number: 11111
In decimal: 31

Solutions:

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

int main ()
{
    char a [9];
    printf ("Enter binary number: ");
    scanf ("%s", a);

    int length = strlen (a) - 1;

    int decimal = 0;
    for ( int i = length; i >= 0; i-- )
        decimal = decimal + (( a [i] - '0' ) * (int) pow ( 2, length - i ));

    printf ( "In decimal: %d\n", decimal );

    return 0;
}