Point out the error in the program

#include<stdio.h>
int f(in

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;
 }

2) What will be the output of the program in 16 bit platform (Turbo C under DOS)?

#include<stdio.h>
int main()
 {
     int fun();
     int i;
     i = fun();
     printf("%d\n", i);
     return 0;
 }
 int fun()
 {
     _AX = 1990;
 }

3) 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);
 }

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

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

5) What will be the output of the program?

#include<stdio.h>
int addmult(int ii, int jj)
 {
     int kk, ll;
     kk = ii + jj;
     ll = ii * jj;
     return (kk, ll);
 }
int main()
 {
     int i=3, j=4, k, l;
     k = addmult(i, j);
     l = addmult(i, j);
     printf("%d, %d\n", k, l);
     return 0;
 }