C Pointers

What Is Pointer

A Pointer is a variable that holds the address of another variable. In C, many complex tasks can be done only with pointers.

Syntax - Pointers

data_type *variablename;

Declaring Pointer variable

• Pointer variables are always declared with asterisk (*) appended to a variable.
• The data type can be int, char, float, long and double.

Pointer Variable Examples

int *iptr; //Integer Pointer variable
long int *iptr; //long int Pointer variable
char *iptr; //char Pointer variable

Addressing Pointer Variables

int i = 5;
int *iptr; //Declaring pointer variable
iptr = &i ; //Initializing address of variable i to pointer variable iptr

The above segment illustrates that, the pointer variable is initialized by an address of integer variable i.

Dereferencing Pointer Variable

Dereferencing is an operation performed to access the value at particular address pointed to by a pointer. The operator * is used to returns the value stored at particular address. The operator * is known as value at address operator or dereferencing operator or indirection operator.

Program - Pointers

#include <stdio.h>
#include .<string.h>
int main()
{
int i = 5;
int *iptr;
iptr = &i;
printf("Value of i = %d ", i);
printf("\nAddress of i = %u", &i);
printf("\nValue of iptr = %d ", *iptr);
printf("\nAddress of iptr = %u", &iptr);
return 0;
}

Advantage of pointer

• Without pointers, dynamic memory allocations are impossible.
• When data type of particular data is unknown, then pointer can be used to access the data regardless of data types as pointers holds only address which is of integer data type.
• Pointers are not just to refer existing variable with its address. Pointers are to interact directly with the hardware, simply one cannot write a data to the device drive without using pointers.
• Pointers can be used to change the value permanently to a variable because pointer access the address of a variable.
• Pointer provides an alternate way to access array elements.
• Pointers are used to create complex data structures.

Disadvantage of pointer

• Pointers are unsafe because its easy for a pointer to get you wrong.
• Uninitialized pointers will cause segmentation fault.
• Improper handling of pointers in dynamic memory allocation will leads to memory leaks.
• Its very hard to debug pointer issues. So using pointers effectively will reduce head ache.
• Though pointer syntax looks awesome i.e) *ptr. when you start appending more asterisks with pointer variable will makes you insane.
• Pointers are 2X time slower than normal variables.

Did You Know?

Asterisks( * ) and address( & ) of operators are similar to positive and negative in mathematical point of view, which means appending * and & simultaneously to the pointer variable will cancelled by itself and just returns the address stored in it.
i.e) *( &iptr ) == iptr

Program - Asterisks and Address of Operators in Pointer Variable

#include <stdio.h>
#include .<string.h>
int main()
{
int i = 5;
int *iptr;
iptr = &i;
printf("\nAddress of i = %u", &i);
printf("\nAddress of iptr = %u", &iptr);
printf("\nAddress of i = %u", *&iptr);
return 0;
}

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