Concept of Pointers:
Every storage location of memory has an associated address. The address is a number that grows sequentially. For every program placed in memory, each variable or function in the program has an associated address.
The address of operator:
The address of operator or Reference operator is denoted by the notation &. When the user wants to get the address of a variable, then the reference operator & can be used. The operator & is used to find the address associated with a variable.
The syntax of the reference operator is as follows:
This means that the address of the variablename is achieved.
The output of the above program could be one of the following, and at each run it differs slightly:
The &exf has the address associated with the integer variable exf and the &test has the address associated with the integer variable test which are displayed using the cout statement.
Using the understanding of address of operators, the discussion turns to the concept of pointers.
exforsys = 100;
test = exforsys;
x = &exforsys;
Using the above information, the assignment takes place as below:
exforsys is an integer variable having the value of 100 stored in memory address location 3501.
When the variable exforsys is assigned to the variable test in the second statement:
test = exforsys;
The value of the variable exforsys 100 is copied to the variable test.
In the third statement, the address of the variable exforsys is denoted by reference operator &exforsys is assigned to the variable x as:
x = &exforsys;
The address of the variable 3501 and not the contents of the variable exforsys is copied into the variable x. The pointers concept fits in this statement. Pointers are the variables that store the reference to another variable. Pointers are variables that store the address of the variable that it is pointed by. Variable x is referred to as the pointer in the above example.
The programmer must note that the address operator placed before a variable is not the same as operator & placed after the variable. For example, &x is not same as x&. Variable &x refers to address operator whereas x& refer to reference operator&.
Pointer is a variable that holds the address, also called pointer variable.
Defining Pointer Variables or Pointer:
In order to define pointer variables, the programmer must use the operator denoted as * in C++.
The symbol * when placed before a pointer, variable means that it as a pointer to.
While defining variables, the data type is placed before it. When the programmer wants to define the integer variable i it is written:
A programmer may think that to define pointer variable there is a separate data type. But this is not the case. There is no separate data type for pointer available. When a programmer defines a pointer variable, he or she can point to integer, float, char. The compiler must know the type of data the pointer is pointing to.
To define pointer variable is as follows:
datatype_of_ variable_pointedto* pointer_varaible;
This defines that ch is a pointer variable which points to char data type.
This defines that i is a pointer variable which points to int data type.
This defines that f is a pointer variable which points to float data type.