Iterate variable (newbie)

Just starting C, so I have some problems with the basics!

I have several inputs and need to identify the largest inputted number.
I am told by my teacher to use a loop.

so far I have this

Code:

---

                float n1, n2;

        while (n1 >= 0)
        {
                printf("Enter any number: \n");
                scanf("%f", &n1);
                printf("Enter any number: \n");
                scanf("%f", &n2);
                /* Reads two numbers */
                if (n1 > n2)
                        max = n1;
                else
                        max = n2;
                /* Compare the two numbers, keep the higher number. */
        }
        printf("Largest number is: %f", max);

---

I want the program to stop running and outputting the highest number if 0 or a negative number is inputted.
I see the potential bug with n1 >= 0 with that n2 can be typed in as a break parameter.

Should I possibly pull the n1, n2 outside the while loop and then keep the 'max' inside the loop ?

If you want to end the loop if n2 is also >= 0 you will do:

Code:

---

while (n1>=0 && n2>=0) {
  ...
}

---

And you HAVE to initialize n1 (and n2 if you use the above code). If you don't it will automatically initialized, so it might be <0 in the begining. You should do:

Code:

---

float n1=1, n2;

---

Thanks C_ntua

I continued work, and I think I have simplified it a bit:

Code:

---

int main(void) {
        float n1, max=0;

        while (n1 > 0)
        {
                printf("Enter any number: ");
                fflush(stdout); /* Compiler won't stop to print line */
                scanf("%f", &n1);
               
                if (n1 > max)
                        max = n1;
        }               

        printf("Largest number is: %f", max);

        return EXIT_SUCCESS;

---

But now it won't stop t ask me for a input?

I don't want to initialize n1 since it can be any positive number and I risk initializing it higher than the inputted number.

Code:

---

int main(void) {
        float n1, max=0;
       
                printf("Enter any number: ");
        fflush(stdout);
        scanf("%f", &n1);

        /* Putting the input outside the loop, I make sure n1 is never
        * a random number and will always continue to the while loop*/
       
        while (n1 > 0)
        {
                printf("Enter any number: ");
                fflush(stdout); /* Compiler won't stop to print line */
                scanf("%f", &n1);
               
                if (n1 > max)
                        max = n1;
        }               

        printf("Largest number is: %f", max);

        return EXIT_SUCCESS;

---

I put another line outside the loop, but I think it looks a bit untidy... is there any way of simplifying this, so I don't have repeating-lines?

edit: Oddly, it reads the decimal numbers as the highest numbers, if I type number like 25 and 0.25 it will read out the 0.25 as the higher number. If I only use integers, it works as intended?

You could initialise max to the same as the first number entered, and then at the end test to see if max is <= 0. If so, output a message saying that no numbers were input instead of the highest number.

A variable must always have a known value before you test it .... attempting to test an undefined variable is asking for undefined behaviour :)

The part outside the while loop isn't used. As far as I can see, it reads a number, then goes to while-loop, reads a new number and works on that number, but forgets to work on the first number I typed in.

I added a line to max = n1 and now is working as intended, thanks Driver!

Code:

---

int main(void)
{
      int n1, max=0;
      printf("Enter any number (0 to end): ");
      fflush(stdout);
      scanf("%f", &n1);
->    max = n1;

while ...

---