Pointers

Question 1

pointer

Answer 1

a variable that stores the memory location of another variable . a pointer has it’s own address

Question 2

assigning and retrieving pointers

Answer 2

int age=22; - assigning a variable age
int ptr=&age; - storing address of variable age at a variable ptr (say 2010)
int _age=ptr; - retrieving corresponding data stored pointer 22

“*” - value of address
“&” - address of

int *ptr for integer
char *ptr for character
float *ptr for float

Question 3

Format specifier for pointers

Answer 3

printf(“%p”,&age); -address of age
printf(“%p”,ptr); -address of age
printf(“%p”,&ptr); -address of pointer

%p -pointer address hexadecimal
%u -unsigned integer numbers

Question 4

Methods to print data at the addresss pointed by pointer

Answer 4

printf(“%d”,age);
printf(“%d”,ptr);
printf(“%d”,(&age));

Question 5

Pointer to pointer

Answer 5

a variable that stores the memory address of another pointer

int **pptr;
char **pptr;
float **pptr;

Question 6

retrieve initial value from **pptr

Answer 6

int main() {
int i=22;
int *ptr=&i;
int **pptr=&ptr;

printf("value of i is :\n%d",**pptr);

Question 7

Pointers in Function call

Answer 7

Call by value- passing value of variable as argument
Call by reference- passing address of variable as argument

if use call by value then changes made to the argument won’t be reflected in the original function to do that we use call by reference

void square(int n);
void _square(int *n);
int main() {
int number=4;
square(number);
printf(“value after is %d\n”,number);
_square(&number);
printf(“value after is %d\n”,number);

}
void square(int n){
n=nn;
printf(“value of n is %d\n”,n);
}
void _square(int n){
*n=(n)(n);
printf(“value of n is %d\n”,n);
}

if we use call by value then only a copy of the argument is send and not the original therefore changes are made in this copy and not the original .being a copy the address of the original and that of the copy will be different.

void printaddress();
int main() {
int n=4;
printaddress(&n);
printf(“address of n is : %u\n”,&n);

}
void printaddress(int *n){
printf(“address of n is :%u\n”,n);
}
printing address of a variable outside and inside a function called by reference

Question 8

swap two numbers a and b by using
-call by value
-call by reference

Answer 8

int swap(int a,int b);
int _swap(int *a,int *b);
int main() {
int x=3,y=4;
swap(x,y);
printf(“value of x and y is %d %d\n”,x,y);
_swap(&x,&y);
printf(“value of x and y is %d %d\n”,x,y);

}
int swap(int a,int b){
int t=a;
a=b;
b=t;
printf(“value of a and b is %d %d\n”,a,b);

}
int _swap(int a,int b){
int t=a;
a=b;
b=t;
printf(“value of a and b is %d %d\n”,a,b);

}

Question 9

return multiple values from a function

Answer 9

you cannot return multiple values from a function ,only one value but you can change the value of multiple variable(defined in the main function) from inside the function itself by passing pointer of these variables as arguments

void do_work(int a,int b,int *sum,int *prod,int *avg);
int main() {
int a=5,b=3,sum,prod,avg;
do_work(a,b,&sum,&prod,&avg);
printf(“sum :%d product :%d average :%d”,sum,prod,avg);

}

void do_work(int a,int b,int *sum,int *prod,int *avg){
*sum=a+b;
prod=ab;
*avg=(a+b)/2;
}

Question 10

max of two numbers using pointers

Answer 10

include<stdio.h></stdio.h>

void maximum(int a,int b,int *max);
int main() {
int a=56,b=11,max;
maximum(a,b,&max);
printf(“max of %d and %d is %d”,a,b,max);

}
void maximum(int a,int b,int *max){
if(a>b){
*max=a;
}
else{
*max=b;
}
}

Question 11

print elements of an array in reverse order

Question 12

print all letters of english alphabet using a pointer

Answer 12

include <stdio.h></stdio.h>

int main() {
char *alpha=”abcdefghijklmnopqrstuvwxyz”;

for (int i=0;alpha[i]!='\0';i++){
    printf("%c\t",alpha[i]);
} }