Question

I know that #define replaced before the compiling to real values. so why the first code here compile with no error, and the 2nd not?

the 1st;

#include <stdio.h>
#include <stdlib.h>
int main()
{
   printf("bc");
   return 0;
}

the 2nd(not working);

#include <stdio.h>
#include <stdlib.h>
#define Str "bc";
int main()
{
   printf(Str);
   return 0;
}

error: expected ')' before ';' token

thank you for the answers, and sorry about my poor English…

Answer 1

Because the Str macro evaluates to "bc"; — the semicolon is included. So your macro expands to:

printf("bc";);

You do not need to follow a #define with a semicolon. They end at a newline, rather than at the semicolon like a C statement. It is confusing, I know; the C preprocessor is a strange beast and was invented before people knew better.