So I working on a program that is supposed to accept all letters and make the vowels uppercase. the problem I am having is the isvowel part. I am not sure how to make it work correctly. I think I have the basic structure down, and am probably missing something minor to get it to work. I am a newbie so any help would be greatly appreciated. Oh and I am not sure how to make the or symbol with my computer so that would probably be a good start to helping me.

here's what I have

Code:
#include <ctype.h>

int main(void)
{
int c, isvowel();

while ((c=getchar()) !=EOF)
if (is vowel(c))
putchar(toupper(c));
else
putchar(c);
return 0;

int isvowel(c)
{...}