Global Function: If any function is declared and defined outside the main() function then this is known as global function. It doesn't matter that global function are only predefined we by ourself can also create the global function. Global function is just the kind of function we can call them from any part of the program. Local function are restricted outside the curly braces i.e.{}we cant call them from outside their area of focus

User Defined Function: If the programmer gives definition to the function according to his  need then this function is known as the user defined function. Predefined function means the the function which is already defined in language dictionary and we use them to implement our ligic.