Pointers Definition | Declaration and Initialization in c programming msbte

Definition Of Pointer

Pointer is a variable which stores memory address of other variable.
Pointer in C is a user defined data type. It is build by using primary data types. Variables hold values and pointers hold their memory addresses where these variables are located in memory.
A pointer variable is therefore nothing but, a variable that holds address of another variable in memory.Memory address is a positive number so its type is unsigned integer. Since pointer is a variable it is also stored at another location in memory and the values stored in it are of unsigned integer type.
The values whose addresses are stored in a pointer variable can be of type char, int, float, double, etc.Let's see how to declare the variables and initialize address of variable to it.

In the program pointers are declared at same location where we declare variables i.e. in declaration section.Declaring a pointer is somewhat similar to declaring a variable.
To indicate which type of value is stored in a variable we use data type while declaring a variable. e.g. to hold integer type of value the data type of variable should be integer, to hold a character the data type of variable should be char and to hold real number the data type of variable should be float or double.
Similarly while declaring a pointer; we should know the data type of the value to which it is going to point, so that we can declare a pointer of that data type. This means suppose a pointer stores address of a variable of type integer then we declare pointer as integer.
Syntax
The syntax of pointer declaration is as follows

   data_type *pointer_name;

  int *ptr;

Here int is the data_type of pointer and ptr is the name of pointer. While declaring the pointer, same guidelines and rules should be followed for pointer_name as given for variable_name in variable declaration.
The above example tells that the pointer ptr is of type integer which means it stores the address of an integer variable in memory

  char *cptr;
  float *fptr;

Here char *cptr specifies that cptr points to character type of value. This cptr pointer will be stored at a specific memory location.

  float *fptr;

will going to point a float value and this fptr pointer will be stored at a specific memory location.

After declaring the pointer, the next step is to assign the address of certain variable to it .This is called as pointer initialization. It connects variables and pointers.
Syntax
Syntax for initializing a pointer.

  pointer_name = &variable_name;

Variable_name is the name of that variable to which the pointer pointer_name will point.
Example
Suppose variable a is an integer. Then initializing the address of a to a pointer can be done in the following way:

  int *ptr; 
  int a; 
  ptr = &a;

In above statements, the first line we have declared pointer ptr of integer type.
In second line we have declared an integer variable a.
And in the third line, the address of a is assigned to the pointer ptr. That's why now the pointer ptr is pointing to the variable a as shown in Fig Below

Fig 1

Suppose the variable a stores at location 2000 and the pointer variable ptr is located at location 5000.
Here ptr=&a; is used to give the address of a to ptr variable so in the memory at location 5000 ,the 2000 is copied.
The dashed line says that the ptr points the value located at location 2000.
As variable declaration and initialization can be combined in single statement, in the same way the declaration of pointer and initialization of pointer can be combined in one statement as follows:

int *b = &a;

Consider a is an integer which holds an integer value 5. So above statement states that the pointer variable b variable holds the address of an integer variable a.
Another examples of pointers are:

char ch='A';
char *q;
q=&ch;

Here the first statement initializes the character A to variable ch. In second statement char *q means q is a pointer that will point character value stored in variable ch. It can be represented in Fig. Below

Fig 2