#include <stdlib.h>
#include <stdio.h>
 
int main ()
{
 
 
 
    int nextDigit,oneDigit;
    char binaryNumber;
    //prompt user for binary #
    printf("Please enter a binary number\n");
    scanf("%c", &binaryNumber);
    /*assign variable decimalValue 0*/
    int decimalValue=0;
 
 
    /*obtain variable nextDigit
    (the first digit in the binary number, then the next and so on.)*/
 
 
    oneDigit=getchar();
 
    if (oneDigit != 1 || oneDigit != 0)
    printf("invalid binary digit was entered.\n");
             else
             {
                     while (oneDigit == '1' || oneDigit == '0');
                           {
                           /*assign variable decimalValue
                           the value of (decimalValue*2)+nextDigit*/
                           decimalValue = ((decimalValue*2) + oneDigit);
                           }
                           printf("%i",decimalValue);
             }
system("PAUSE");
return 0;
}

int ch = getchar() ; // reads a char literal '0', '1' etc.
// the integer contains the code point for the literal (depends on the charset)
// to convert it to an integer digit with value 0, 1 etc. 
if( isdigit(ch) )
{
    int digit = ch - '0' ;
    /* use digit */
}

printf("Please enter a binary number\n");
    scanf("%c", &binaryNumber);