Post on 02-Jan-2016
description
Objects Methods and Properties
ProgrammingProgramming is the act of writing instructions
that tell a computer how to do something.
Sending a Simple Instruction to a Computer
I want the computer to shut down
How would I do this?(Use of my senses)
How would I tell one of you to do it?(Use of natural language)
How do we tell the computer to turn itself off?
Natural Language and Computers“ok computer turn your self off now”
Does the computer understand the words we have used?
Strong regional accents?
Consider the following…Off computer turn nowOK puter turn thesel ov nowCmptr trn yrslf ff nw
Natural language allows for ambiguity and imprecision
Computers are really quite thick
Symbols and MeaningWe use symbols all of the time in our daily life
“Represents” the tune “three blind mice” but it isn’t the tune
South Nottingham CollegeHigh Road Beeston NG9 4AH
Represents the address but it isn’t the place
Which Code is Correct? Dim MyAge As Integer MyAge = 23 If MyAge > 21 Then lblError-Text = "You are old enough" End If
Or…
Dim MyAge As Integer MyAge = 23 If MyAge > 21 Then lblError.Text = "You are old enough" End If
Computer ProgrammingWe want to create:
A system that accurately identifies the individual components in a computer so we may control them
A system that may be used to set the sequence of instructions such that they are carried out in the way we intend
A system of representation that is easy to maintain avoiding unnecessary duplication and excess baggage
Something that is reasonably easy for us as human beings to write and understand (we don’t want the symbols to get in the way of the meaning)
Objects, Methods, Properties Lots of new terms to understand
Objects provide tools for referencing and controlling bits of the computer
Methods tell objects to do somethingProperties control the settings of an object
Cuba the Cat - MethodsRelease - let
Cuba outsideFeed - give
Cuba some food
Scoop - clean up after Cuba
Methods make the object do something
Cuba the Cat - PropertiesLegs 4Tails 1Ears 2Fangs 3
Properties tell us how the object is set up
The Computer as an ObjectWe want to represent and control the
computerView the computer system as a set of objects
MyComputer.TurnOff()
MyComputer represents the entire computerTurnOff is a method that turns the computer
off
Important Key ConceptsObject A way of representing computer
technology so that we may control it
Method Used to tell an object to do something
Property Used to find out or control something out about the
object, i.e colour.
Overview
Programming is the act of writing instructions that tell a computer how to do something
We need a standard system of notation allowing us to represent what the computer is to do that makes
reasonable sense to human beings