Glossary of programming terms
Object:
A collection of data which represents something, and contains information or data about the object.
It can also have methods (see Methods) which can manipulate the objects’ data
Example:
A car=>
- Colour
- Make
- Engine Size
- Engine Revs
- DriveCar()
A car has properties (see properties) and DriveCar() is a method operating on the car.
Here, Make, Colour and Engine size are constant but Engine revs is variable as you DriveCar().
Method:
A function (see Functions) contained within an object which can alter values of the object.
Example:
A car=>
- Colour
- Make
- Engine Size
- Engine Revs
- DriveCar()
A car has properties (see properties) and DriveCar() is a method operating on the car.
Here, Make is a constant but Engine revs is variable as you DriveCar().
Colour and EngineSize are usually constant once a car is made, but can be changed if need be.
These are often called PseudoConstants.
Function:
A routine which performs and operation on data and can return the result.
A general function may look like this: myfunction( x, y){ return x*y}
Example: function area( width,height){ return width * height}
And to use it: mysquare=area( 30, 40)
So mysquare now equals 1200 (30*40)
In the car example we have a Method called DriveCar(): this is an internal function which does not return anything.
We could have another method function which returns a value: lets add a method GetRevs() and define it as returning the engine revs.
GetRevs(){ return EngineRevs)
MyCar=>
- Colour=Red
- Make=Ford
- Engine Size=1500
- Engine Revs=0
- DriveCar( )
- GetRevs()
So now when we use the new function we will be told EngineRevs:
currentRevs=MyCar=>GetRevs()
currentRevs=10,000 rpm
Functions can also take Arguments (see Arguments), so for example we could define DriveCar to take a speed:
MyCar=>DriveCar( speed )
So we have:
MyCar=>
- Colour=Red
- Make=Ford
- Engine Size=1500
- Engine Revs=0
- DriveCar( speed )
- GetRevs()
And to set car speed we use it thus:
MyCar=> DriveCar( 50 )
Variables and Constants:
A user defined data type which can hold the results of functions or preset value.
In the Car example we have 2 variables Colour and EngineSize. These are both things which a car owner can change or vary.
The Car Make is not changeable by the owner once it has been made, so Make is considered a Constant.
MyCar=>
- Colour=Red
- Make=Ford
- Engine Size=1500
- Engine Revs=0
These are all attributes of the car.
(Note properties and attributes terms are often used interchangeably)
Attribute:
A property of an object which holds a value.
Example:
MyCar=>
- Colour=Red
- Make=Ford
- Engine Size=1500
- Engine Revs=0
These are all attributes of the car.
(Note properties and attributes terms are often used interchangeably)
Constructor:
A collection of attributes which instruct object creation.
To create a car you need to have a Car template or Class, then to construct a new Car you can use the basic default Car class and modify it as it is constructed.
Example:
MyNewCar= new Car( Colour=Red, Engine_size=1500, Make=Ford )
So the new car will look like this:
MyNewCar=>
- Colour=Red
- Make=Ford
- Engine Size=1500
- Engine Revs=0
- DriveCar()
Here EngineRevs is not set so it takes the default of 0 from the Car class template.