nested while loop help

I'm creating a program that will test a range of temperatures for validity. I have become stuck, in this case am trying to print a message saying invalid input when a user enters a value not in the range of 425 - 435.

Code:

#include <stdio.h>
#define sentinel 999

int 
main(void)
{
    int temp;
    double valid;


    printf ("Enter the number 999 when you are finished entering numbers.\n\n");
    printf ("Enter the temperature range :", sentinel);
    scanf("%d", &temp);


    while (temp != sentinel ) {
           valid = 1;
    while (valid) {
            if (temp > 425 && temp < 435)
                valid = 0;
    }
        printf("The product cure temperature is good!\n");
        break;
    }


    return (0);
}

Put your printf, and scanf() for temp, inside the first while loop (and before the second while loop).

I wouldn't use the variable "valid" for testing, in both while loops.

Code:

if(temp == sentinel)
   break;

in the outer while loop seems sufficient. That reduces the outer while loop to just while(1), with the printf()'s, and the scanf() for temps, and with the above if(test==sentinel), test in it.

Keep valid for the nested while loop, and keep it simple. Not really needed here, but don't be afraid in C, to use a small function for things like a nested loop. Small and simple functions make getting the logic right, *much* easier, and easier to alter, etc., when you need to.

Why would you make a simple flag variable a DOUBLE? Taking up eight bytes of memory and then messing with floating point values just for a single 1 or 0 value?

Instead, why not:

Code:

while (temp > 425 && temp < 435) {
    scanf("%d", temp);
    if (temp == sentinel) break;
}

Or something like this, you can add the print statements.

Thanks guys ^^ i understand it better now. ill try and see if i can get the hang of this am still pretty new to C. ill come back if i still dont get it :P

Sorry to bother again. i changed the code a bit thanks to your advice. i just can't figure out how to make it print input is invalid.
can you please show a fixed version of my code and explain what you did? am still a noob at c.

Code:

int main(void)
{
    int temp;
    int testing;




    printf ("Enter the number 999 when you are finished entering numbers.\n\n");
    printf ("Enter the temperature range:", sentinel);
    scanf("%d", &temp);
    
    if (temp < 425 && temp > 435) {
        printf("your input is invalid range is 425 - 435");
    }


    while (temp != sentinel ) {
        testing = 1;
    while (testing) {
            if (temp >= 425 && temp <= 435)
                testing = 0;
    }
        printf("The product cure temperature is good!\n");
        break;
    }




    return (0);
}

Originally Posted by Oo Kami

Sorry to bother again. i changed the code a bit thanks to your advice. i just can't figure out how to make it print input is invalid.
can you please show a fixed version of my code and explain what you did? am still a noob at c.

Code:

int main(void)
{
    int temp;
    int testing;




    printf ("Enter the number 999 when you are finished entering numbers.\n\n");
    printf ("Enter the temperature range:", sentinel);
    scanf("%d", &temp);
    
    if (temp < 425 && temp > 435) {
        printf("your input is invalid range is 425 - 435");
    }
....
}

What exactly is your condition asking and is it what you really want to check? Take a look at If Statements, specifically look at the boolean operators AND (&&) and OR(||).

Thanks you just taught me || means or with that i was finally able to print a message if a user enters values not in the range of 425 - 435.

Code:

	while (temp != sentinel ) {
		if(temp<425 || temp>435) {
			printf("Warning! AT risk!\n");
			exit(0);
		}