Question

#include<stdio.h>

typedef struct student{
int id;
int mark;
}stud;

typedef struct stud *s1;

void main(){
s1 = NULL;
printf("hi");
}

Please help me how to initialize struct pointer to NULL. i get the following error during compilation.

graph.c: In function ‘main’:  
graph.c:11:04: error: expected identifier or ‘(’ before ‘=’ token

Answer 1

You meant to define the variable s1 as

stud *s1;

Live demo: http://ideone.com/9ThCDi

The reason you got the error you did is that you were declaring s1 to be a type for “pointer to struct stud”. This is wrong for two reasons:

1. You didn’t want s1 to be a type; you wanted it to be an object.
2. Your struct was struct student. But you defined an actual type called stud.