quartz/content/notes/12-pointers-to-routines.md

title	aliases	tags	sr-due	sr-interval	sr-ease
12-pointers-to-routines		cosc204 lecture	2022-09-08	3	250

compiler ⇒ converts high level language description of program into assembly description of the program assembler ⇒ converts assebly language description into machine code description loader ⇒ loads program into memory, loaded at $4000

data has an address in memory, so does the application. Therefore functions must also have an address in memory which we can access

pointers to routines

int (*method)(int param)

to assign a pointer to a routine

method = square;

to call the routine

result = method(6);

basic example

pointer as member of a struct;

pointers to routines can beused anyqhere variables can

• member of struct

• parameter to other routine

modules

we can break programs into functional modules

• each modules excapsulates one behaviour
• give us a way of data hiding

add pointer to structs as parameters to methods in modules

• call this an abstract data type ADT
• we communicatre with an ADT via its public interface
  • so that the implementation details are hidden

method in this struct are "black box"

we gain

• abstraction
  • our queue has a print method, so could out stack, tree, and so on
  • we call ob->print() without needing to know (exactly) which print method is called

constructor

creates object, initialises it and sets up function pointers

destructor

good to use. help with closing things and freeing memory

modules overview

c programs consist of .c and .h files

• put ADT declarations in the .h (header) files
  • we can #include these files if we want to use the ADT in a program
• put routine implementations in .c files

queue header

pragma says include only once: prevent include loops