Beginning question about While loops

Hello! So I'm currently trying to teach myself C via the Internet, and I'm stuck on the While loop. Here's what I'm trying to do: the user should input a non-negative number no greater than 23; if the number is greater than 23, then the prompt should let the user try again and then re-evaluate the new number to see if it's a non-negative number.

Here's what I have:

Code:

---


#include <cs50.h>
#include <stdio.h>

int main(void)
{
    printf("Insert a non-negative integer no greater than 23: ");
   
    int x = GetInt();
    while (x > 23)
        printf("Insert a non-negative integer LESS than 24!: ");
        x = GetInt();

    while (x < 0)
        printf("Insert a NON-NEGATIVE integer less than 24!: ");
        x = GetInt();

    return 0;
}

---

However, when I run the program and type in 28 for example, it's an infinite loop and does NOT ask for another integer (no GetInt(); activated), which I don't understand because in my while loop, I state that the prompt should allow the user to type in another number and then evaluate to see if it should get out of the while loop.

What am I doing wrong? Thank you!

1. Your first problem is that you need braces around your loop. Omitting braces means the next single statement is looped over.

What happens right now is equivalent to this:

Code:

---

int main(void)
{
    printf("Insert a non-negative integer no greater than 23: ");
   
    int x = GetInt();
    while (x > 23)
    {
        printf("Insert a non-negative integer LESS than 24!: ");
    }
    x = GetInt();
 
    while (x < 0)
    {
        printf("Insert a NON-NEGATIVE integer less than 24!: ");
    }
    x = GetInt();
 
    return 0;
}

---

In the actual body of the loop, GetInt() is never called - x never changes throughout the while loop, so it infinitely loops because it never gets a new x to evaluate.

2. You also have a second problem - you want to check both conditions in a single loop, not in two separate loops. Consider the || operator, which takes two boolean (conditional) statements and combines them such that the result is true if either of the conditions is true.

Also, I forgot to include this, but: I know you can easily execute this code using the do-while loop, but I want to do it using the While loop. Thank you.

C does not care about indentation, so you need to add braces to do what you want

Code:

---

while (...) {
  statement1;
  statement2;
  ...
  statement_n;
}

---

Got it! Thank you so much, Cat! That makes so much more sense. You're freaking awesome.