Higher Computing Science Variable Scope

1. Variable Scope

2.  A variable declared within a sub-program (procedure or
function) is known as a local variable and has local
scope
 It is only recognised within the sub-program in which it
has been declared
 The variable can only be changed by code within that
sub-program
Local Variable

3.  A variable declared as global in the main program has
global scope
 It can be recognised and changed across the entire
program
 This might not be an issue in smaller programs, but can
be a problem in larger programs.
WHY?
Global Variable

4. Scope Example

5. Are Global Variables Bad?
Generally speaking, global variables are considered bad,
especially in larger programs.
If you declare a global variable, it’s harder to keep a track
on what changes are made to it across different parts of
the program. It makes it difficult to debug errors.

6. Are Global Variables Bad?
Generally speaking, global variables are considered bad,
especially in larger programs.
If you declare a global variable, it’s harder to keep a track
on what changes are made to it across different parts of
the program. It makes it difficult to debug errors.