Declaring Variable as Constant

The values of some variable may be required to remain constant through-out the program. We can do this by using the qualifier const at the time of initialization.

Example:

Const int class_size = 40;

The const data type qualifier tells the compiler that the value of the int variable class_size may not be modified in the program.


Volatile Variable

A volatile variable is the one whose values may be changed at any time by some external sources.

Example:

volatile int num;

The value of data may be altered by some external factor, even if it does not appear on the left hand side of the assignment statement. When we declare a variable as volatile the compiler will examine the value of the variable each time it is encountered to see if an external factor has changed the value.