Transcript PowerPoint
IMAT1604 Visual Web Development
About me…
Matthew Dean
[email protected]
http://www.tech.dmu.ac.uk/~mjdean/
(Or Google mjdean dmu)
Stuff to memorise this Week
"A function is a section of
code that does one thing
well"
What is an Object Anyway?
What is a word?
Think about the following word…
Shop
What springs to mind?
A Specific Shop
The act of shopping…
Creating Instructions
A word on its own isn’t much use to us however when
we combine it with other words we can create
instructions.
“I want you to go to the shop and get me a tin of peas.”
Words are Really Just Symbols
What is this?
What if we add other symbols?
Traffic lights and words on a page are all the same they
are all symbols that we look at and assign meaning.
What is Programming?
Programming is about using words and symbols to
communicate with a Computer
As with our example above we use words / symbols to
create instructions or functions that the computer will
follow and perform some task.
Functions are organised into classes – text files
Who is this?
More to the point why is she so irritating?
We need to use the right words correctly
Most of us end up feeling more like
this...
The Importance of Vocabulary
“Shop, street, road, post box, lamp post, post code, house, flat,
house number, left, right ahead, distance, time, street sign,
landmark.”
These words make up the vocabulary of the streets and
roads. We are familiar with these words and can easily
make up instructions (functions) using these words.
“You want to walk down that street for 10 meters then turn left
at the post box. You will then see a sign to the railway
station. Follow that sign for 5 meters and the shop is on the
left.”
Computer Programming
Introduces a new Vocabulary
“Class, object, assignment, sequence, variable, RAM,
parameter, data type, function, method, property,
selection, sequence, integer, string.”
The Computer Programmer
The person who knows how to write the correct words
/ symbols to tell the computer what to do
Computers copy and process data
Data is made of binary numbers
Nobody really likes binary
We need a set of commands to control data
First Look at Some C# Code
What is wrong with this?
The Problem
Computers are really fussy
Spotting errors can be difficult at first
This gets easier with practice
Take a look at the following…
Int32 Name;
Name();
“Name”
.Name
//Name
(Name)
-
Variable
Function
A string of letters
A method or a property (Probably a property)
A comment
A parameter
New Terms to Understand
Function
Method
Property
Class
Instantiation
Object
Functions
“A function is a section of code that does one thing
well.”
Methods and Properties
Method
A function that tells the object to perform an action
E.g. Multiply
Property
A function that allows us to get or change the settings of
an object
E.g. Count
(This will be confusing at first!)
Classes
A class is a text file that contains related functions making them
easier to manage
Classes are like recipe books
Recipe books dedicated to specific regions
Classes dedicated to specific sets of functionality
A student manager class might contain…
Methods
.AddStudent
.UpdateStudent
.DeleteStudent
Properties
.Count
.HighestStudentGrade
So what is an Object Anyway?
An object may be thought of as simply a word that
means something to the computer
The object in this code is MyStudents
Made up by the programmer
Associates the word with the class file clsStudents
Allowing us to access the function/method AddStudent
Instantiation
Stuff in green called comments
Create an object MyCompter referencing the code in
the class file clsComputer
Invokes the function/method TurnOff
Instantiation is the act of creating an object
Summary
Programming is the act of writing lists of words that control the data in
the system
We need a system for writing lists of instruction for the computer that
makes reasonable sense to human beings
We also have some key words for you to start getting to grips with…
Function
Property
Method
Class
Object
Instantiation
A function is sequence of words that instruct the
computer to perform a single action on some data
well
A property is a function that tells us about or sets
some aspect of the data
A method is a function that changes the data in
some way
A class is a collection of related functions in a text
file
An object is a word that references the code in the
associated class
The process of linking an object to a class