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Types of Pointers in C

Pointers in C

A pointer is a variable and this variable 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 runtime. Pointer variable can access the value that is outside of the function body.

For eg. 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

There are various types of pointer in C, to put a number on it, we have 8 different types of pointers in C. They are as follows

1) Void pointer  2) Null pointer  3) Wild pointer4) Dangling pointer
5) Complex pointer6) Huge pointer7) Near pointer8) Far pointer

1) Void pointer

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.

Declaration:   void *ptr = NULL;

Example:

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


printf(“%d”, *ptr);
return 0;
}

Use of Void pointer

The built functions like malloc and calloc functions (which are used for allocation of memory) returns a void pointer. Due to this reason, they can allocate a memory block for any type of data.

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 a Null pointer.

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

Example:

#include<stdio.h>
int main()
{
int *ptr = NULL;
return 0;
}

Use of Null pointer

  1. Used when 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. The inefficiency occurs because  they may point to some unknown memory location which may cause a program to perform unintended actions or may even lead to program crash..

Example:

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

4) Dangling pointer

A dangling pointer is another type of pointer and it is a pointer which points to some non-existing memory location.

This situation arises when a pointer is pointing at the memory address of a variable but after some time that variable is deleted from that memory location while the pointer is still pointing to it.

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 within a given section of that computer memory which is 16 bit enabled.

Example:

#include<stdio.h>
int main()
{
   int x = 25;
   int near* ptr;
   ptr= &x;
   printf(“%d”,sizeof ptr);
   return 0;
}

8) Far pointer

A far pointer is typically 32 bit which can access memory outside that current segment. It is similar to a huge pointer but a far pointer is fixed and hence that part of that sector within which they are located cannot be changed.

Example:

#include<stdio.h>
int main()
{
  int x= 10;
  int far *ptr;
  ptr=&x;
  print(“%d”, sizeof ptr);
  return 0;
}

Conclusion

A pointer is a variable and this variable 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).

Pointers in C are difficult to understand for beginners but it is an essential part of programming in C. They are various types of pointers and each type has its own benefits. It is important to learn and understand the various types in order to grab a good grip on this topic.



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