Local variables are declared within sub-programs and can only be accessed and modified within that sub-program. Global variables are declared in the main program and can be accessed and modified by any code in the entire program. While global variables can be recognized program-wide, they should generally be avoided as the code is harder to read, debug, and track which parts are updating the variable.

1. VARIABLE SCOPE
Higher Computing Science

2. LOCAL VARIABLES
• Declared within the sub-program
• Only recognised in the sub-program in which the variable is declared
• Can only be changed by code in the sub-program in which the variable
is declared

3. GLOBAL VARIABLES
• Declared as global in the main program
• Can be recognised and changed by any code in the entire program
• Should be avoided, especially with large programs
• Hard to keep track of which code updates the global variable
• Makes code more difficult to read
• Logic errors caused by code unexpectedly changing the value of a global
variable, and harder to debug

4. VARIABLE SCOPE
• Local variable scope: the sub-program in which it is declared
• Global variable scope: the entire program