It might help to be less confusing if you interperet = as gets and == as is

for Example try looking at your code like this:

PHP Code:

```
#include <stdio.h>
```

#include <math.h>

int square(int);

int main(void){

int num;

printf("Hello, World!\n");

num = square(5); /* num gets the value of 5 squared */

printf("5 squared is is %d\n\n", num);

/* and extra example */

if ( num == 22){

printf("Num is 22\n");

}

else

printf("Num is not 22, it's really %d", num);

getchar();

return 0;

}

int square(int n){

return(n * n);

}

Also. My math is pretty bad but your function returns the square of n. if you want the square root of a number. Include <math.h> an use the the sqrt() function.

Hope that helps a bit.