Point out the error in the program

#include<stdio.h>
int main

Point out the error in the program

#include<stdio.h>
int main()
 {
     int a=10;
     void f();
     a = f();
     printf("%d\n", a);
     return 0;
 }
 void f()
 {
     printf("Hi");
 }

2) Which of the following statements are correct about the function?

long fun(int num)
 {
     int i;
     long f=1;
     for(i=1; i<=num; i++)
         f = f * i;
     return f;
 }

3) What will be the output of the program?

#include<stdio.h>
int check(int);
int main()
 {
     int i=45, c;
     c = check(i);
     printf("%d\n", c);
     return 0;
 }
int check(int ch)
 {
     if(ch >= 45)
         return 100;
     else
         return 10;
 }

4) What will be the output of the program?

#include<stdio.h>
void fun(int*, int*);
int main()
 {
     int i=5, j=2;
     fun(&i, &j);
     printf("%d, %d", i, j);
     return 0;
 }
 void fun(int *i, int *j)
 {
     *i = *i**i;
     *j = *j**j;
 }

5) How many times the program will print "Study 2 Online" ?

  #include<stdio.h>
  int main()
 {
     printf("Study 2 Online");
     main();
     return 0;
 }