FUNCTIONS SUMMARY

Parameter pass by copy  - needs extra space for copy
			- takes time to copy
			- use for small data

Parameter pass by ref	- address operator & on objects
			- function works on caller's object directly
			- unsafe, may change owner's data

Use const to pass by ref
			- function cannot change owner's object

Inline function		- compiler does not create func code
			- rather expands within caller's code
			- faster execution
			- why create such func? For readability!

Default param

Function prototype declaration

Recursive function, driver

Function overloading

Template function	- pros and cons

Scope, Named scope, Using namesapace