Man scanf and read the documentation carefully. You also need to consider how to provide information with your question. You don't even mention the language. This is for C. C++ has overloaded pow functions.
Code:
#include <stdio.h>
#include <math.h>

int main()
{
    double base = 2.0;
    double exp;

    while (1)
    {
        printf ("Enter the exponent: ");
        if (scanf ("%lf", &exp) == 1)
        {
            printf ("2 raised to the power of %f is %f\n", exp, pow (base, exp));
        }
        else 
        {
            printf ("Invalid input.  ");
            break;
        }
    }
    return 0;
}
Quote:
Originally Posted by Output
Enter the exponent: 4
2 raised to the power of 4.000000 is 16.000000
Enter the exponent: 16
2 raised to the power of 16.000000 is 65536.000000
Enter the exponent: