Question

Pointer (76%) Pointer is a (historical) concept used in C (and C++), but not in any other computer languages. Due to C language’s being prevalent however, you need to learn about this. Pointer concept is explained in detail in the power point file of chapter 7 (slides 12, 20 etc. for example). 1. (12%) Printing a variable and its pointer. Consider the C instruction: int p = 0, *pptr = &p; Write a C program that prints the int variable p and its pointer pptr. Show the output (and turn in the C code, but not the 10M bytes project folder). 2. (16%) Show four (4) different ways that you increment the variable p by 1, where one of them uses *pptr or the dereferencing of pptr. 3. (24%) pointer to pointer: pptr is a pointer to the int variable p. Can there be a pointer to pptr? If that is doable, write code and show the output. If that is not doable since C language does not support (not because you do NOT know how to do that), explain! 4. (12%). Can there be two pointers to the same variable? You see that pptr points to the int variable p. Can there be a second pointer variable p2pptr also pointing to p as well? Explain! 5. (12%) Can the same pointer pptr be used to point to a different variable q (= 3) for example? Explain!

Answer 1

Answer 1:

C code:

#include<stdio.h>

void main(){
int p = 0;
int *pptr = &p;

printf("p = %d\n",p);
printf("pptr = %d",pptr);
}

Here p would print the value and pptr would print the address of the p.

Output:

Answer 2:

Different ways to the incerement value of p

#include<stdio.h>

void main(){
int p = 0;
int *pptr = &p;

printf("p = %d\n",p);

p = p + 1;
printf("p = %d\n",p);
p++;
printf("p = %d\n",p);
++p;
printf("p = %d\n",p);
*pptr = *pptr + 1;
printf("p = %d\n",p);
(*pptr)++;
printf("p = %d\n",p);
++(*pptr);
printf("p = %d\n",p);
}

Output:

Answer 3:

Yes pointer to pointer is doable in c, please find below code

Code:

#include<stdio.h>

void main(){
int p = 0;
int *pptr = &p;
int **ppptr = &pptr;

printf("p = %d\n",p);
printf("Address of p: %d\n\n",&p);

printf("p = %d\n ",*pptr);
printf("Address pointed by pptr: %d\n",pptr);
printf("Address of pptr: %d\n\n",&pptr);

printf("p = %d\n",**ppptr);
printf("Address pointed by ppptr which is address of pptr: %d\n",ppptr);
printf("Value pointed by ppptr which is address of p: %d\n",*ppptr);
}

You can see from the output the relation between p, *pptr and **pptr

Output:

Answer 4:

Yes, there can be two pointers that can point to the same variable. It means both of them can update the value of the variable and access.

Code:

#include<stdio.h>

void main(){
int p = 0;
int *pptr = &p;
int *p2pptr = &p;

printf("p = %d\n",p);
printf("Address of p: %d\n",&p);
printf("p = %d\n",*pptr);
printf("p = %d\n",*p2pptr);
printf("Address pointed by pptr: %d\n",pptr);
printf("Address pointed by p2pptr: %d\n",p2pptr);

}

Output:

Answer 5:

Yes, pptr can point to another variable. But at a time it can save only one address. So, once you update the address in the pointer it will update the pointing location. At a time pointer can't point to 2 locations.

#include<stdio.h>

void main(){
int p = 0;
int *pptr = &p;

printf("p = %d\n",p);
printf("Address of p: %d\n",&p);
printf("p = %d\n",*pptr);

int q = 0;
pptr = &q;

printf("q = %d\n",q);
printf("Address of q: %d\n",&q);
printf("q = %d\n",*pptr);
}

Output: