2. Introduction
Storage class explain the behavior of the variable in
terms of scope and lifetime, it also determine the
initial of the variable.
Scope of the variable is the region over which the
variable is visible or valid.
Life time of the variable is the time during which
memory is associated with the variable.
Initial value is the value assigned to the variable
implicitly if no value is assigned to it by the
programmer.
3. There are four types of storage class available in C:
Auto
Extern
Static
Register
4. Auto
All local variables has this storage class.
Default value is the garbage value.
Scope of the variable is only between the blocks
where it is declared.
Lifetime is till the control remains within the block
or function where these variables are defined.
These variables are destroyed whenever block ends
or function jump occur.
To declare auto storage class auto keyword is used.
5. Example:
auto int n;
Auto keyword is optional all the local variables by
default fall under this storage class.
Example:
int n;
6.
7. Extern
Scope is through out the program.
Lifetime is till the end of the program.
Initial value is 0.
Extern keyword is used to declare the variable of this
storage class.
extern int x;
By default global variable has this storage class.
8.
9. Static
It is special case of local variable.
These are defined inside the function or block.
Its scope is inside the block or the function where it
is defined.
Initial value is 0.
Its value is retained between different function calls.
Lifetime is same as the global variable i.e. through
out the program.
Keyword static is used to define this type of variable.
10.
11. Register
Register variable behave in every way same as the
auto variable.
The only difference is that register variable are store
inside the computer register instead of the memory.
They are used when CPU has to access the variable
very frequently. Eg looping variable
They are defined by placing keyword register before
the datatype of variable. Example
register int a=10;
