C Variables

A variable is just a named area of storage that can hold a single value (numeric or character). The C language demands that you declare the name of each variable that you are going to use and its type, or class, before you actually try to do anything with it.
                                                                                                                                    

The Programming language C has two main variable types 

1. Local Variable
2. Global Variable 

Local Variable :

• Local variables scope is confined within the block or function where it is defined.Local variables must always be defined at the top of a block.  

• When a local variable is defined - it is not initalised by the system,you must initalise it yourself.  

• When execution of the block starts thevariable is available, and when the block ends the variable 'dies'.

Check following example's output

This will generate following output
i is 5
i is 100
i is 5

Here ++ is called incremental operator and it increase the value of any integer variable by 1. Thus i++ is equivalent to i = i + 1;

You will see -- operator also which is called decremental operator and it idecrease the value of any integer variable by 1. Thus i-- is equivalent to i = i - 1;

Global Variables :

• Global variable is defined at the top of the program file and it can be visible and modified by any function that may reference it.

• Global variables are initalised automatically by the system when you define them!

Data Type	Initialiser
int	0
char	'\0'
float	0
pointer	NULL

If same variable name is being used for global and local variable then local variable takes preference in its scope. But it is not a good practice to use global variables and local variables with the same name.

This will generate following output

Value of i = 11 -- func() function
Value of i = 5 -- main function

i in main function is global and will be incremented to 5. i in func is internal and will be incremented to 11. When control returns to main the internal variable will die and and any reference to i will be to the global.