Variable attributes: Visibility - Scope - Lifetime

Ø  Variable Attributes:

Ø  Visibility:

Ø  void func()

       {

        int x;

        {

         // x is visible here

        }

       }

Ø  void func()

       {

        int x;

        {

         int x;

         // outer x is not visible here

        }

       }

Ø  Scope:

è Global scope – file scope – function scope – block scope

è In the previous example:

Ø  outer x scope is its block (outer block)

Ø  but it is not visible in the inner block (due to inner block variable with the same name)

Ø  Life Time:

è For local variables:

Ø  static: lifetime = program time

Ø  automatic: life time = function time

Ø  dynamic: malloc() and free()

è For global variables (global and file local)

Ø  lifetime = program time