Thread: Exponential Problem with C Programming

Hey guys, I'm new to C programming, taking a course for EE.

This is the question: C does not have an exponentiation operator. Write a C program that allows the user to enter the base a and the exponent b and prints the value of (a^b). You may not use any library functions other than printf and scanf. Assume b is an integer.

So I have my program but when you input a and b, it seems like it hang ups, no output. When you press enter many times, it doesn't do anything. Only when you input something (when you are not suppose), does it display the printf statement.

Can anyone help me out? thanks

here is the code:

Code:

#include <stdio.h>
int main ()
{
	int b,i;
	float a,c;

	printf("\nEnter base value a: ");
	scanf("\n%f", &a);
	printf("\nEnter exponent value b: ");
	scanf("\n%i\n", &b);

	c=1;
	i=1;	

	while(i<=b)
	{
		c*=a;	
		i++;
	}
	

	printf("\nThe answer is %.2f", c);

	return(0);
}

The code

Code:

scanf("\n%i\n", &b);

does not do what you think it does. Namely, the \n at the end means to throw away whitespace, but the program needs a non-whitespace character (later) to know when to stop throwing away the whitespace. So: don't put \n at the end of a scanf format string, unless you know positively there will be more input coming and want (for whatever reason) to make sure there's no whitespace in the input buffer. (Note: this will never happen.)

what do you mean by whitespace?

whitespace = things that print "white" on a piece of paper. So: spaces, tabs, carriage returns, line feeds, form feeds, and the ever-popular vertical tab (\v). The \n at the beginning is alright; but whitespace is always skipped by scanf unless you're explicitly reading in characters with %c (or doing some extra-fancy things).

If the base b is allowed to be negative, then you need to handle that case as well, by first computing the answer for the corresponding positive value, then taking the reciprocal. You can worry about that after getting it working for nonnegative values of b, though.

Edit: Another way to handle it is to simultaneously take the reciprocal of a, and reverse the sign of b, which is probably easier.

You might want to look in the <math.h> header. There's a function called pow() that might prove very useful for what you're doing.

thanks for all your help