Asterisk Histogram - Infinite Loop

Hi guys. I wrote a small program where the user inputs a number and the program prints the number in asterisks. I used a for loop for this. However when I put the for loop inside a while loop to keep looping the program, it goes into an infinite loop. I just can't seem to figure out what the problem is.

Without the while loop the for loop works perfectly, printing out the asterisk(s). It's when I add the while loop that things get ugly.

Code:

#include <stdio.h>

int main(void)
{

	int number, counter;
	printf("Enter number: ");
	scanf("%d", &number);

	while (number > 0){
		for (counter = 0; counter < number; counter++){
			printf("*");
		}
	}

}

Yep, sure will... because the exit condition is never met. You need to count down your number variable until it hits 0.

Would you care to explain what you mean by count down my number variable?

I can't use break statement's either. I need to exit this loop, but exit how?

Originally Posted by Tony92

Code:

#include <stdio.h>

int main(void)
{

	int number, counter;
	printf("Enter number: ");
	scanf("%d", &number);

	while (number > 0){
		for (counter = 0; counter < number; counter++){
			printf("*");
		}
	}

}

When does the condition in red ever evaluate to false? What is the value of number in your while loop? When does it change?

Ah I see what you are saying. The printf is outside the loop so more user input cannot go through the program am I right?

When does is it ever false? When number is less than 0
What is the value of number? Whatever the user inputs
When does it change? Never I believe.

Originally Posted by Tony92

When does is it ever false? When number is less than 0

Actually when number is 0 or less, but you get the picture.

Originally Posted by Tony92

What is the value of number? Whatever the user inputs

ok.

Originally Posted by Tony92

When does it change? Never I believe.

So if number never changes in your while loop why do you expect your while loop to end? Note you never ask for another number to be inputted in your while loop.

Yeah I figured that out. The thing is if I put my input statements inside my while loop, the first time the program runs it won't run properly. A Do-While loop will work but the outline says I should use a pre-test loop.

So ask the user once before the loop, then again as the last thing inside the loop.

There we go I fixed it, tell me what you think.

Code:

#include <stdio.h>

int main(void)
{

	int number = 1, counter;
	
	
	while (number > 0){
        printf("Enter a number: ");
	    scanf("%d", &number);
		for (counter = 0; counter < number; counter++){
			printf("*");
		}

	}


}

Yep, that works too. Hopefully the instructions say not to use a do-while loop so you can see just how stupid it is to do something like this with a pre-test loop. This is exactly when you should use a do-while.

Seems like you got it. I would also recommend that you return an integer at the end of "main()" - typically zero for normal program termination.

Yeah it was really irritating me, it specifically said to use a pre-test loop and I think you're right it's to show when exactly is the time to use a do-while. Thanks for your help guys.

Originally Posted by Matticus

Seems like you got it. I would also recommend that you return an integer at the end of "main()" - typically zero for normal program termination.

Oh yes I almost forgot about that.

1. You define main as returning an int correctly, however you forgot to actually return one, e.g. return(0);

Other than that, good work. Just keep in mind the way you have your loop setup if the user enters zero to quit your program will still evaluate the for-loop before exiting. Not a big problem for this case however loop logic can become tiresome. For example you could have done:

Code:

#include <stdio.h>

int main(void)
{

	int number, counter;
	
	printf("Enter a number: ");
	scanf("%d", &number);
	
	while (number > 0){
		for (counter = 0; counter < number; counter++){
			printf("*");
		}
		printf("Enter a number: ");
	             scanf("%d", &number);
	}

	return (0);
}

EDIT: Holy rapid fire posts while I was typing mine up.

That is true.

One question the return 0; why did you add brackets around the 0? I was taught that it was only return 0; and not return (0);