DAY 1

Problem solving session on Pointers

1. Below program demonstrates the following:

1. How to declare a pointer variable(s)

2. How to assign address into pointer variable 3. How to access the value thru pointer variable

int main()

{

char c = 'p';

int i = 10;

// pointer variable declaration

char *cptr; // points to character

int *iptr; // points to integer

//assignment of pointer variables

cptr = &c;

iptr = &i;

printf("[%c][%d]\n",*cptr,*iptr);

return 0;

}

Check out the results …..

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2. Explore what happens if integer pointer is assigned to character pointer!!!

int main()

{

//Declaration

int i = 256; char *cptr;

//Assignment using casting

cptr = (char*)&i;

//Result

printf("[%d]\n",*cptr);

return(0);

}

3. Learn how OS allocates the memory for different data types using sizeof()

function

int main()

{

char c;

int i;

long int li;

float f;

double d;

char *cptr;

int *iptr;

long int *liptr;

float *fptr;

double *dptr;

Page 2 of 12

printf("size of char[%d]\nsize of int[%d]\nsize of long int[%d]\n size

of float[%d]\nsizeof double[%d]\n",

sizeof(c),sizeof(i),sizeof(li),sizeof(f),sizeof(d) );

printf("\n\nsize of char ptr[%d]\nsize of int ptr [%d]\nsize of long int

ptr[%d]\n

size of float ptr[%d]\nsizeof double ptr[%d]\n " ,

sizeof(cptr),sizeof(iptr),sizeof(liptr),sizeof(fptr),sizeof(dptr) );

return 0;

}

4.Find out the usage of const keyword

int main()

{

//Declaration const int i = 10;

const int *cptr = &i;

i = 20;

*cptr = 30;

//Guess what happens …..

printf("i[%d] cptr[%d]\n",i,*cptr);

return 0; }

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5. Understand the usage of void pointer exhibited in the following

program:

int main()

{

char c= 'p';

int i = 10; float f = 10.5; void *vptr;

vptr = &c;

printf("[%c]\n",*(char*)vptr);

vptr = &i;

printf("[%d]\n",*(int*)vptr);

vptr = &f; printf("[%f]\n",*(float*)vptr);

return 0; }

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6. Following program explains the usage of incremental operator on

pointers:

int main() {

char s[] = "protech";

char *ptr; ptr = s;

// print the address of ptr printf("[%u]\n",ptr);

//increment ptr by 1

ptr++

// Print the address of ptr once again

printf("[%u]\n",ptr);

return 0; }

7. Understand the usage of assignment operator on pointers: int

main() {

int a, *ptr1,*ptr2;

a = 10;

ptr1 = &a;

ptr2 = ptr1;

printf("[%d]\n",*ptr2);

return 0;}

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8. In the following programs, there will be an error while

compiling/ executing. Understand the error -

Program 1:

#include<stdio.h>

int main()

{

int a = 10;

int *ptr; ptr = NULL;

printf(“[%d]\n”,*ptr);

ptr = &a;

printf("[%d]\n",*ptr);

return 0; }

Program 2:

int main()

{

int a = 10; void *ptr = &a;

printf("[%d]\n",*ptr);

return 0; }

Page 6 of 12

9. Explore while loop on pointers:

int main() {

char company[] = "protechsoft technologies pvt ltd"; char *ptr;

ptr = company;

while(*ptr) printf("%c",*ptr++ );

printf("\n");

return 0; }

10. Using above concepts, write a program which copies 2 strings.

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Problem solving session on Pointers

Following programs may have ERROR(S) - Rectify & execute -

1. int main() {

int i = 256;

unsigned char *cptr; cptr = &i;

//Get the output

printf("[%d]\n",*cptr);

}

2. int main(){

int i = 10;

int a[] = {1,2,3}; int *const ptr = &i;

printf("a[%d]\n",a[0]);

a = ptr;

ptr++;

a++

printf("a[%d]\n",a[0] );

return 0; }

Page 8 of 12

3. int main()

{

int i = 5;

char c[] = {"ProtechSoft"}; char *ptr;

ptr = c;

ptr = ptr + 2;

printf("[%s]\n",ptr);

ptr = ptr + i;

printf("[%s]\n",ptr);

return 0;

}

4. int main()

{

char c[] = {"ProtechSoft"};

char *ptr; ptr = c; ptr1 = ptr1 + 4;

printf("[%s]\n",ptr1);

ptr1 = ptr1 - 12;

printf("[%s]\n",ptr1);

return 0;

} Page 9 of 12

5. int main()

{

unsigned char s[] = "ProtechSoft"; char *cptr;

cptr = s+6;

printf("[%c]\n",*cptr);

s++;

printf("[%c]\n",*cptr);

s--;

printf("[%c]\n",*cptr); return 0;

}

6. void main()

{

int a[] = {10,20,30,40,50};

int *ptr; ptr = a;

printf("[%u]\n",ptr);

ptr++;

printf("[%u]\n",ptr);

} Page 10 of 12

7. void main()

{

int a = 10,b = 20;

int *ptr1,*ptr2;

ptr1 = &a;

ptr2 = ptr1;

if(ptr1 == ptr2)

printf("Your Comments - 1\n");

ptr2 = &b; if(ptr1 < ptr2)

printf("Your Comments - 2\n");

if(ptr1 > ptr2)

printf("Your Comments - 3\n");

if(ptr1 != ptr2) printf("Your Comments - 4\n");

}

8. void main()

{

int a, *b, c[10];

a= -100;

b = &a;

c[0]= a;

c[9] = *b + 101;

c[1] = *(c+9)++;

*c = *b--;

printf(“%d\t%d\n”,*c,*(c+1));

}

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9. void main()

{

char a, *b, c[3];

a= 0xaa;

b = &a;

c[0]= a;

c[9] = *b + 10;

c[1] = *(c+9)++;

*c = *b--;

printf(“%s\n”,c); }

10. void main() {

unsigned char a, *b, c[2];

a= 0xab;

c = &a;

b = *c;

c[0] = *b + 10;

c[1] = *(c+9)++;

*c = *b--;

printf(“%s\n”,c);

}

Page 12 of 12