Scope Basics

Scope is a term that refers to a variables accessibility and existence. While a variable is in scope it is stored in the computer's memory. Its value can be accessed and manipulated. When a variable goes out of scope it is erased from the computer's memory and its value can no longer be accessed or manipulated.


The easiest way to think about scope is that a variable has the scope of the block it is declared in.
Blocks are defined by opening and closing curly braces. A variable declared in the class block has class scope. It can be seen and used by any method in the class. A variable that has method scope can be seen and used by any command in the method. A variable that has block scope, such as in an if block or a loop,
can only be accessed from within that block.

Below is example of various scopes: (it is not a real program and won't run. It is just to show the levels of scope.)

---

class program
{
   int number; //class scope
  
   static void Main()
   {
      string name; //method scope

      number=0;//changing the class level variable

      while (number==0)
      {
         int counter=1; //block scope
      }

   } 

}

---

A couple of other things to note. If you name two variables the same, the one with the smaller scope takes precidence. That means if I have a class level variable named number, and I name a variable in one of my methods number, the variable is given method level scope for the duration of the method,

There are some exceptions to the general scope rule but we will deal with them as we encounter them.

General Principle

Give any variable the most limited scope possible, while still enabling it to do what it needs to do.