Subroutines, Global Variables and Parametres

Subroutines, Global Variables and Parametres

1. Parametres

   • A parameter is a value that is being passed in or out of a block of code. Parametres can be passed into a program in two ways
     • By Value
       • Used when a value needs to be passed into a program but does not need to be passed out again
       • The fromal and actual parametres have diffrent memory locations when a parametre is passed by value. (A new memory location is made for the formal parametre
     • By Refrence
       • Used when a value will be passed into a program, updated and then passed out again
       • Arrays are always passed by refrence
       • The formal and actual parametres share the same memory location when the parameter is passed by refrence

2. Subroutines

   • It is often more efficient to split up a program into modules called subroutines. These can then be used in any order, and more than once if need be.
     • This makes the code more efficient, and saves time in both writing and correcting the code. The below image shows an example of were time is saved by re-using subroutine "validate"

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