一元'*'的无效类型参数

Question

I'm a week into an intro programming class, and I'm having trouble with fixing what's supposed to be a relatively simple code. I keep getting an invalid type argument of unary '*' error.

#include <stdio.h>
#define PI 3.14159; 
int main()
{
   float r;
   float area;
   scanf("%f", &r);
   area = PI * r * r;
   printf("Area is %f", area);
   return 0; 
}

Could someone explain this, and how to fix it?

Answer 1

#define PI 3.14159; 
                  ^

Drop the semicolon. Leaving it in, the code will expand to:

area = 3.14159; * r * r;

Answer 2

You have to remove the extra ; in the definition of the macro PI . It is unnecessary for macro, and in your case results in syntax error after expansion.