Pointer

Pointer is a variable that points to or references a memory location where data is stored. Each memory cell in the computer has an address which can be used to access its location. A pointer variable points to a memory location rather than a value. It has two parts: the pointer itself holds the address and the address point to a variable.

Some of the uses/advantages of pointer are

1.     Pointers are more efficient in handling array and data tables.

2.     Pointers are necessary for dynamic memory location.

3.     They can be used to return multiple values from a function via function arguments.

4.     Implementing data structure like linked lists, trees, graphs, queues, stacks.

5.     Pointers reduce length and complexity of programs thus increases the execution speed and reduces the program execution time.

6.     Use of pointer array to character string results in saving data storage in memory.

The pointer declaration syntax:

            pointer_type    *pointer_variable_name;

For example:    int *p;

Address (&) and Indirection (*) Operator

The & operator and immediately preceding variable returns the address of the variable associate with it. Hence, the address of (&) operator returns the address of memory location in which the variable is stored.

The indirection(*) operator is used to extract value from the memory location stored in the particular memory location whose address is stored in pointer variable

            pointer_variable = &variable_name;

For example:

            int * ptr, num=25;

            ptr =#

Places the memory address of num variable into the pointer variable ptr

If we want to find out the value stored in the ptr variable then,

*(ptr); or  *(&num);

Explain the meaning of each of the following declaration

1)     int *p : - pointer to an integer

2)     int *p[10]:-pointer to an array of 10 integer.

3)     int(*p)[10]:- *p is an array of size 10;

4)     int *p(void) :- function doesn't pass any value to the pointer function p since it has void arguments

5)     int *p(char*a):-this function pass the memory address if the character variable to pointer variable p since it has * a arguments.

Difference between Array and Pointer

Array	Pointer
Array is a static memory allocation. Once memory is allocated, it cannot be resized or freed dynamically.	Pointer is a dynamic memory allocation. The memory allocation can be resized or freed later.
Array cannot access the value of pointer	Pointer can access the value of the pointer.
Execution speed of the program is slow in comparison to pointer.	Execution speed of the program is very fast.
Array refer data value in memory location	Pointer refers address to the memory location.
Array can be initialized at definition. Example int num[ ] = { 1,2, 3}	Pointer can’t be initialized at definition.

Similarities between Array and Pointer

1.     Two pointer variables cannot be added and pointer variable cannot be multiply by a constant similarly two array variables cannot be added and array variable cannot be multiply by a constant.

2.     Pointer can holds the memory addresses of multiple variables of same data type and array can hold the value of similar data type.