Validate integers helps ~

[Siaw Ys]

#include <stdio.h>
#include <ctype.h>
  
    int main(void)
    {
        int size, i;

        do {

            printf("Enter class size (<50): ");
            scanf("%d", &size);

        } while(!isdigit(size));

        for (i=0; i <size; i++)
        {
        
        }
        
  
        return 0;
    }

Why my code can't validate integers? Very thanks you.

[CommonTater]

You need to check the returned value from scanf() to determine if the conversion failed or not...
Presetting your variable to an impossible value also helps...

do
  { size = 0;
    printf("Enter class size (1 to 50) : "); }
while( (scanf(" %d",&size)  < 1) || (size < 1) || (size > 50) );

Look up scanf() in your C Library Documentation for more information. (If you don't have it, get it...)

[Siaw Ys]

Thanks ~ But could you tell me where could I found the c documentation? Because I never view before so I don't know where to search for it...this sound noob but....

[CommonTater]

Go to the home page for your compiler... You should be able to download compiler and library specific documentation there.

If your compiler doesn't have it... get another compiler.

Pelles C, comes with help files that contain the full documentation. (In POIDE all you do is put your text cursor on a keyword and press F1.)

[rags_to_riches]

Or go to Google and type in "man <whatever the function name is>"

You have the entire Internet at your disposal...use it!

[CommonTater]

Or go to Google and type in "man <whatever the function name is>"

You have the entire Internet at your disposal...use it!

I don't disagree... but it's always preferable to have the exact compiler specific documentation whenever possible.

Going back to the Pelles C example... there are several hundred non-standard functions available in various libraries that you would never know about without the help files Pelle provides.