puzzle code of pointer

Q1) Output of the program.
#include "stdio.h"
#include "conio.h"
main()
{
      int a=10,*p,**q,***r;
      p=&a;
      q=&p;
      r=&q;
      printf("%d",*(*(*r))+5);
      getch();
}

Ans:-15

Q2) Output of the program.
#include "stdio.h"
#include "conio.h"
main()
{
int a[][3]={
             {1,2,3},
             {4,5,6},
             {7,8,9}
           };
printf("%d",  *(*(a+1)+1));     
getch();
}
Ans:-5
Discussion:-

Q3) Output of the program
#include "stdio.h"
#include "conio.h"
void print()
{
     printf("sourav");
}

main()
{
  void (*p)();    //Pointer of function declaration.
  p=print;          //Function address assignment to pointer.
  p();                 //Function call.
  getch();
}
Ans:-sourav
Discussion:-Here p is a pointer of function print(); And the print() is called by p().

Q4)Output of the program.
#include "stdio.h"
#include "conio.h"
main()
{
   int a[2][2][2]={1,2,3,4,5,6,7,8};
   printf("%d ",   *(*(*(a+1)+1)+1));
   printf("%d ",***a);
   getch();
}
Ans:-8 1
Discussion:-here a is a three dimension array. The first printf statement will print 8,the expression is equivalent to a[2][2][2] and second printf statement will print the a[0][0][0] th value of array a.
 
Q5)Is the code Wright.
#include "stdio.h"
#include "conio.h"
#include "stdlib.h"
main()
{
void *p;
p=malloc(100);
getch();
}
Ans:-No
Discussion:-To correct to coding it is need to cast the pointer.  The correct code is p=(char*)malloc(100);

Q6) Output of the program.
#include "stdio.h"
#include "conio.h"
struct abc
{
       int a,b;
 };
struct abc t,*p;
main()
{
   p=&t;
   p->a=10;
   p->b=20;
   printf("%d %d",p->a,p->b);
   getch();
}
Ans:-10 20
Discussion:-Here p is a pointer of structure. p takes the address of a structure variable .and the arrow operator(->) is used to access the member of the structure.

Q7)Output of the program.
 #include "stdio.h"
 #include "conio.h"
main()
{
   char *p="%d";   
   printf(p,500);
   getch();
}
Ans:-500
Discussion:-Here p is a character pointer. And hold the base address of the string “%d”.
In printf function p pointer replace by the string  “%d”.
Q8)Output of the program.
 #include "stdio.h"
 #include "conio.h"
main()
{
   int a[]={10,20};
   int *p=a;
   *p++;
   printf("%d ",*p);
   ++*p;
   printf("%d ",*p);
  getch();
}
Ans:-20 21
Discussion:-The statement *p++ increment the content of p pointer, so it will point the second element of array a. And the statement ++*p will increment the content of p pointer.

Q9)Output of the program.
#include "stdio.h"
#include "conio.h"
#include "string.h"
main()
{
 char *p="sourav";
 char *q="kayal";
 char a[20];
 int k=0;
 while(*p!=NULL)
 {
  a[k]=*p;
  p++;
  k++;
 }
 while(*q!=NULL)
 {
   a[k]=*q;
   q++;
   k++;            
 }
 puts(a);
 getch();
}
Ans:-souravkayal
Discussion:-This is the program of string concatenation using pointer. Here scale factor of character pointer is 1.
Q10) output of the program.
#include "stdio.h"
#include "conio.h"
main()
{
  printf("%d %d",sizeof(NULL),sizeof(""));
  getch();
}
Ans:-It depends upon compiler.
         In xp TC++ environment it prints 2 1
         In window7 , DEV C++ environment it prints 4 1

Q11)Output of the program
#include "stdio.h"
#include "conio.h"
main()
{
   int *p;
   char *q;
   float *r;
   printf("%d %d %d",sizeof(p),sizeof(q),sizeof(r));
   getch();
}
Ans:-Output is compiler dependent
         Xp and TC combination gives 2 2 2
        Window7  and DEV C++ gives 4 4 4.
Discussion:-It depends upon system memory byte size.

Q12)Find out the error.
#include "stdio.h"
#include "conio.h"
main()
{
  int *p;
  *p=100;
  printf("%d",*p);
  getch();
}
Ans:-The program is syntactically correct. But no output will come.
Discussion:-Here p is a integer pointer but not initialize by and address. So in run time it will take random address.



 Q13)Output of program.
#include "stdio.h"
#include "conio.h"
main()
{
 
  struct abc
  {
         int a;
         int b;
  };
  struct abc t,*p;
  t.a=100;
  t.b=200;
  printf("%d",sizeof(p));
  getch();
}
Ans:-Output depends upon platform.
         In XP and TC++ it will give 2
         In Window 7 DEV C++ it will give 4