Practical no.
7
To study and perform program based on the use of Pointers.
Theory:
A pointer is a variable that stores the address of another variable. Unlike other
variables that hold values of a certain type, pointer holds the address of a
variable. For example, an integer variable holds (or you can say stores) an
integer value, however an integer pointer holds the address of a integer variable.
In this practical, we will discuss pointers in C programming with the help of
examples.
C Pointers – Operators that are used with Pointers
Lets discuss the operators & and * that are used with Pointers in C.
“Address of”(&) Operator
We have already seen in the first example that we can display the address of a variable using
ampersand sign. I have used &num to access the address of variable num. The & operator is
also known as “Address of” Operator.
printf("Address of var is: %p", &num);
Point to note: %p is a format specifier which is used for displaying the address in hex format.
Now that you know how to get the address of a variable but how to store that address in some
other variable? That’s where pointers comes into picture. As mentioned in the beginning of this
guide, pointers in C programming are used for holding the address of another variables.
Pointer is just like another variable, the main difference is that it stores address of another
variable rather than a value.
“Value at Address”(*) Operator
The * Operator is also known as Value at address operator.
How to declare a pointer?
int *p1 /*Pointer to an integer variable*/
double *p2 /*Pointer to a variable of data type double*/
char *p3 /*Pointer to a character variable*/
float *p4 /*pointer to a float variable*/
The above are the few examples of pointer declarations. If you need a pointer to store the
address of integer variable then the data type of the pointer should be int. Same case is with
the other data types.
By using * operator we can access the value of a variable through a pointer.
For example:
double a = 10;
double *p;
p = &a;
*p would give us the value of the variable a. The following statement would display 10 as
output.
printf("%d", *p);
Similarly if we assign a value to *pointer like this:
*p = 200;
It would change the value of variable a. The statement above will change the value of a from 10
to 200.
/*C program to demonstrate example of double pointer (pointer
to pointer).*/
#include <stdio.h>
int main()
{
int a; //integer variable
int *p1; //pointer to an integer
int **p2; //pointer to an integer pointer
p1=&a; //assign address of a
p2=&p1; //assign address of p1
a=100; //assign 100 to a
//access the value of a using p1 and p2
printf("\nValue of a (using p1): %d",*p1);
printf("\nValue of a (using p2): %d",**p2);
//change the value of a using p1
*p1=200;
printf("\nValue of a: %d",*p1);
//change the value of a using p2
**p2=200;
printf("\nValue of a: %d",**p2);
return 0;
}
Write a program in C to print all permutations of a given string using pointers.
C Code:
#include <stdio.h>
#include <string.h>
void changePosition(char *ch1, char *ch2)
char tmp;
tmp = *ch1;
*ch1 = *ch2;
*ch2 = tmp;
void charPermu(char *cht, int stno, int endno)
int i;
if (stno == endno)
printf("%s ", cht);
else
{
for (i = stno; i <= endno; i++)
changePosition((cht+stno), (cht+i));
charPermu(cht, stno+1, endno);
changePosition((cht+stno), (cht+i));
int main()
char str[] = "abcd";
printf("\n\n Pointer : Generate permutations of a given
string :\n");
printf("---------------------------------------------------
-----\n");
int n = strlen(str);
printf(" The permutations of the string are : \n");
charPermu(str, 0, n-1);
printf("\n\n");
return 0;
OUTPUT:
EXAMPLE PROGRAM FOR C STRUCTURE USING POINTER:
In this program, “record1” is normal structure variable
and “ptr” is pointer structure variable. As you know, Dot(.)
operator is used to access the data using normal structure
variable and arrow(->) is used to access data using pointer
variable.
#include <stdio.h>
#include <string.h>
struct student
int id;
char name[30];
float percentage;
};
int main()
int i;
struct student record1 = {1, "Raju", 90.5};
struct student *ptr;
ptr = &record1;
printf("Records of STUDENT1: \n");
printf(" Id is: %d \n", ptr->id);
printf(" Name is: %s \n", ptr->name);
printf(" Percentage is: %f \n\n", ptr->percentage);
return 0;
}
OUTPUT:
Conclusion:
In this way we had studied and perform program based on
pointers.
