C Tutorial

C Tutorial C Language Environment Setup Execution flow of C program C printf and Scanf C Data type C Token Variable in C Operators in C Comments in C Escape Sequence in C C – Storage Classes C Decision control statement Loop Statement in C Break, continue and goto statement in C Type Casting in C Function in C Recursion in C String in C C Array Pointer in C Dynamic memory allocation C –Structure Nested Structure in C Union in C File Handling in C C pre-processor Static Function In C Sizeof In C Selection Sort In C Scope Of Variables In C Runtime Vs Compile Time In C Random Access Lseek In C Queue Implementation In C Pseudo Code In C Prototype In C Pointer To Pointer In C Pointer Arithmetic In C Passing Array To Function In C Null Character In C Merge Sort In C Macros In C Library Functions In C Memory Leak In C Int In C Goto And Labels In C Fibonacci Series In C Fflush In C Derived Data Types In C Data Types In C Const Vs Volatile In C Character Set In C Character Class Tests In C Calloc In C C Pointers Arrays In C Include In C Clrscr In C C Vs Java String Literals In C Types Of Pointers In C Variables In C Volatile In C Why C Is A Middle Level Language Infix To Postfix Program In C Ceil function in C LCM of two numbers in C Quick sort in C Static in C function pointer as argument in C Top Array Keywords in C Add two numbers using the function in C Armstrong program in C using function Array, Declaring Arrays and Array Initialization Limitations of Inline Function in C Merge and Merge sort with example in C Do-While Loop in C For Loop in C While-Loop in C Difference between while and do-while loop in C Array Of Structures in C Data Structures And Algorithms in C Types Of Structures In C How to Avoid Structure Padding in C Use of Structure in C Do WHILE LOOP in C Programming Examples For Loop in C Programming Examples Entry Control Loop in C Exit control loop in C Infinite loop in C Nested loop in C pow() function in C String Handling functions in C Prime Number code in C Factorial Program in C using For Loop Factorial Program in C Using While Loop Fibonacci Series in C Using For Loop Fibonacci series in C using while loop Prime Number Program in C using for Loop While Loop in C programming examples Built-in functions in C Assert() Function C vs Java Strings Call Back Function in Embedded C Else If Ladder fgets() function Ftell() Function getc() function getch() function gets() function Heap Sort Nested if-else statement Pi() Function Positioning of file Write() function abs() function in C Attributes in C C program to find factorial of a number using Recursion Ferror() in c fopen() function in C Fibonacci series program in C using Recursion Formatted Input and output function in C Snake Game in C User Defined Functions in C Beep() function in C Cbrt() function in C Hook() function in C Isalnum() function in C C Program to find the Roots of a Quadratic Equation C Switch Statements Difference between rand() and srand() function in C Difference between while and for loop in C Doubly Linked list in C Example of Iteration in C How to use atoi() function in C How to use floor() function in C How to use sine() function in C How to use Typedef Struct in C Integer Promotions in C C Program Swap Numbers in cyclic order Using Call by Reference C Program to Find Largest Number Using Dynamic Memory Allocation C Program to Find the Largest Number using Ternary Operator C/C++ Program to Find the Size of int, float, double and char Find the Largest Three Distinct Elements in an Array using C/C++ Loop Questions in C Modulus on Negative Numbers in C Multiplication table program in C using For loop Nested Loops in C Programming Examples C Program for Mean and Median of an Unsorted Array Results of Comparison Operations in C and C++ Reverse a Stack using Recursion in C Simple hash() function in C strcat() Function in C Sum of N numbers in C using For loop Use of free() function in C Write a program that produces different results in C and C++ C Function Argument and Return Values Keywords in C Bank management system in C Calendar application in C Floor() Function in C Free() Function in C How to delete a file in C How to move a text in C Remove an element from an array in C Unformatted input() and output() function in C What are linker and loader in C fork() in C GCD program in C Branching Statements in C Comma Operator in C Control statement in C Double Specifier in C How to create a binary file in C Long int in C Palindrome Number in C Pure Virtual Function in C Run Time Polymorphism in C Types of Array in C Types of Function in C What is a buffer in C What is required in each C Program Associativity of Operators in C Bit Stuffing Program in C Actual and Formal Parameters Addition of two Numbers in C Advantages of function in C

C Pointers

Pointers in C

A pointer is a variable, which contains the address of another variable, i.e., it’s a variable which has the address of another variable as its value. The utilization of pointers is to access the memory and also, to govern the address (manipulation of address).

A pointer is a derived datatype, which is constructed with the primitive data type. The size of the pointer variable is 2-byte for any data types. The pointer variable allows us to occupy the memory in runtime.

Pointer variable can access the value that is outside of the function body.

For e.g., If a is a variable of type int having value \0 stored at address 3000 and address of a is assigned to some other variable b, then b is a pointer variable pointing to memory address stored in it. In simple words, b is a pointer variable containing the address of a (i.e., 3000).

Types of Pointers in C

We have 8 different types of pointers in C. These are as follows:

  • Void Pointer
  • Null Pointer
  • Dangling Pointer
  • Wild Pointer
  • Complex Pointer
  • Huge Pointer
  • Near Pointer
  • Far Pointer

 

1) Void Pointer in C

A pointer is said to be void when a pointer has no associated data type with it. In other words, it can point to any data type and also, it can be typecasted to any type.

Since a void pointer does not have any standard type (data type) it is also referred to as a generic pointer sometimes.

A pointer can be declared as a void pointer by simply using the keyword void.

Example:

int main()
{
int num = 5;
void *ptr = #


printf(“%d”, *ptr);
return 0;
}

Declaration/ Syntax :

void  *ptr = NULL;

Why Void Pointer?

The malloc function returns a void pointer on successful allocation of memory because the malloc() is not aware of the location it is pointing to.

Declaration

(void* ) malloc(size_t size)

Here, size_t is defined in <stdlib.h> as unsigned int.

Note 1: The malloc function will simply allocate a block of memory as specified in the heap and if it is successful, it returns a pointer which points to the first byte of the allocated memory. In case of failure, NULL is returned.

Note 2: malloc returns a void pointer on successful memory allocation.

Note: There is no support of any kind of arithmetic operation in the concept of void pointers, i.e., it does not provide support for this problem statement. The void pointer will make the use of ‘*’ operator to serve the entire purpose.

Drawbacks of void pointer in C

The above case points out some of the limitations of void pointers. These can be pointed out as follows

  •  Pointer arithmetic is not possible with void pointer due to its concrete size.
  •  It can’t be used as dereferenced.

In order to solve the above problem, there is a requirement to typecast the pointer variable and it is used for dereferencing as well. The limitations of void pointers introduce the need to typecast the pointer variables.

2) Null pointer

Another type of pointer under this classification is Null pointer. It is a special type of pointer that does not point to any memory location. In other words, if we assign a NULL value to a pointer, then the pointer is considered as a Null pointer.

Note: In case of null pointer, it always contains 0 or NULL as its value.

Example:

#include<stdio.h>  //header file


int main()
{
int *ptr = NULL; // declaration of null pointer
return 0;
}

Use of Null pointer

  1. It is used to initialize a pointer when that pointer is not assigned any memory address for that instance of time.
  2. It is useful for handling errors when using in-built functions like malloc function.

3) Wild pointer

A Wild pointer is a type of pointer which is used to point to some arbitrary memory location, that’s why it is referred to as Uninitialized pointers. The wild pointer is uninitialized and due to this, they  are not very efficient. .

Example:

int main()
{
int *ptr;  //This is a wild pointer
*ptr = 5;
return 0;
}

Note: The inefficiency occurs because,

they may point to some unknown memory location. This can cause program crashes.

4) Dangling pointer

Pointer which points to some non-existing memory location.

Example:

int main()
{
int *ptr = (int *)malloc (sizeOf(int));  
…
…
…
free(ptr);  //memory is released


return 0;
}

In the above code, when the free() function is executed, the memory assigned to ptr is released but the pointer is still pointing to the deallocated memory and hence it is called a Dangling pointer.

6) Huge pointer

A huge pointer can access memory outside the current segment and is typically of size 32 bit.

A Huge pointer is not fixed and hence the part within which a huge pointer is located can be changed.

7) Near pointer

A Near pointer is a pointer that is utilized to bit-address up to 16 bits. The near pointer’s 16-bits address is accessible within a given section of that computer memory which is 16-bit enabled.

Example:

#include<stdio.h>  //including header files
int main()
{
   int n  = 07;
   int near* ptr_nr;
   ptr_nr= &n;
   printf(“%d”,sizeof ptr_nr);
   return 0;
}

8) Far pointer

It is a 32-bit pointer and is special pointer because it can access memory outside that current segment.

Example:

#include<stdio.h>
int main()
{
  int f= 55;
  int far *ptr_fr;
  ptr_fr=&f;
  print(“%d”, sizeof ptr_fr);
  return 0;
}

Conclusion

The utilization of pointers is to access the memory and also, to govern the address (manipulation of address).

Pointers in C might be difficult to understand for beginners, but it is an essential part of programming in C.



ADVERTISEMENT
ADVERTISEMENT