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) Point out the error in the program

#include<stdio.h>
int f(int a)
 {
   a > 20? return(10): return(20);
 }
int main()
 {
     int f(int);
     int b;
     b = f(20);
     printf("%d\n", b);
     return 0;
 }

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>
int main()
 {
     void fun(char*);
     char a[100];
     a[0] = 'A';
 a[1] = 'B';
     a[2] = 'C';
 a[3] = 'D';
     fun(&a[0]);
     return 0;
 }
 void fun(char *a)
 {
     a++;
     printf("%c", *a);
     a++;
     printf("%c", *a);
 }

5) What will be the output of the program?

#include<stdio.h>
int check (int, int);
int main()
 {
     int c;
     c = check(10, 20);
     printf("c=%d\n", c);
     return 0;
 }
 int check(int i, int j)
 {
     int *p, *q;
     p=&i;
     q=&j;
     i>=45 ? return(*p): return(*q);
 }