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Pointer Declaration and Definition in c language

In C language, we know that all the variables should be declared before they are used. Pointer variable should also be declared before their use. The syntax to declare a pointer variable is shown below.

type *  identifier;

Type : type can be any datatype such as int, float , char etc. It may be derived or user defined data type also.
*       : The asterisk (*) in between type and identifier tells that the identifier is a pointer variable.
Identifier : Name given to the pointer variable. 

Example -1 : Consider the following declaration:
int * p;
The above declaration can be read as "p is pointer to integer variable" and this declaration informs the following points:

  • The variable p is a pointer variable. So, it should contain the address of variable during execution.
  • The type int refer to the type of the variable stored in pointer variable p i.e. the pointer variable p should contain address of an integer variable.

Example-2 : Consider the following declaration:
double *pd;
This declaration informs the compiler that pd is a pointer variable and can hold the address of a variable of type double.

Example-3 : In the declaration, the position of * is immaterial. For example, all the following declaration are same:
int *pa;
int * pa;
int*  pa;
Any of the above declaration informs that the variable pa is a pointer variable and it should contain address of integer variable.

Example-4 : Consider the multiple declaration as shown below:

int* pa,pb,pc;

Note : Here, we may wrongly assume that the variables pa, pb amd pc are pointer variables. This is because * is attached to int. This assumption is wrong. Only pa is a pointer variable, whereas the variables pb and pc are ordinary integer variables. For better readability, the above declaration can be written as shown below:

int *pa, pb, pc;

Now, we can easily say that pa is a pointer variable because of * operator, whereas pb and pc are integer variables and are not pointer variables. It is still better if the variable are declared in separated lines as shown below:
int *pa;
int pb;
int pc;


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Memory representation of Linked List

             In memory the linked list is stored in scattered cells (locations).The memory for each node is allocated dynamically means as and when required. So the Linked List can increase as per the user wish and the size is not fixed, it can vary.

               Suppose first node of linked list is allocated with an address 1008. Its graphical representation looks like the figure shown below:

      Suppose next node is allocated at an address 506, so the list becomes,

  Suppose next node is allocated with an address with an address 10,s the list become,

The other way to represent the linked list is as shown below:

 In the above representation the data stored in the linked list is “INDIA”, the information part of each node contains one character. The external pointer root points to first node’s address 1005. The link part of the node containing information I contains 1007, the address of next node. The last node …