ND Unit 06

Types of Programming Language

This session will cover:

Procedural languages Object-orientated programming Visual languages Mark-up languages Scripting languages

To Pass assignment 1 you must describe 4 different types of language [P1]

Procedural Languages

Early Windows programs used these The program controls what happens

not the user The task is completed based on user

input Tasks are broken into a number of

stages known as procedures or subroutines

Procedural Languages

Each procedure does a specific part of the task

For example a procedure might open a file, read in a number or multiply 2 numbers

Examples are C, Fortran, Pascal, and Basic

Object-orientated programming (OOP)

Is relatively new and not used until the 1990’s when programs got more complex

The program is broken down into objects, not lists of instructions

Each object can perform tasks and communicate with other objects

The object can be thought of as a small machine with a set job

Object-orientated Example

A company’s personnel records program would have an employee object

The employee object would have features such as Forename Surname and date of birth – we call these attributes

The object would also have actions such as join company, leave company, change details – we call these methods

Object-orientated programming (OOP)

Unlike procedural programming, the programmer does not need to know the code which is ‘behind’ each object making it work

They only need to know the attributes and methods of each object and how to make it interact with other objects

They then use the objects as ‘building blocks’ to make the program do what they want it to

Examples languages capable of OO are Java, C# and VB.NET

Visual Programming Languages

These are used to create software which has a graphical user interface (GUI), such as Windows programs

VP languages have procedural features but also have OO capabilities

Examples of VP languages are Visual Basic.NET and Visual C++

Visual Programming Languages

VP design has 2 stages First the programmer

designs the GUI, placing objects such as textboxes, buttons and labels onto a form

Then they write the code which gives the functionality to the program

Markup Languages

A markup language combines text and extra information about the text

This extra information is in the form of tags

Tags control the structure or presentation of the text – should it be large or small font, blue, green, bold or underlined?

The programmer can also insert images, hyperlinks and tables into the text using tags

Markup Languages The best-known markup example is

Hypertext Markup Language (HTML), used on the World Wide Web

Example: <title>Home Page</title> <style type="text/css" media="screen"> @import "stylesheets/public.css"; body { background-color: white }; </style> Another example is XML (Extensible

Markup Language) which allows users to write their own tags

Scripting languages

Scripting languages can be typed in directly from a keyboard

Some are used to execute a series of commands that would otherwise have to be typed in via a keyboard / mouse

These can be used to control the operating system and are known as a shell script language

Examples are VBScript and Windows Powershell

Scripting languages

Others allow users to write short, simple, programs

Often the language used is specific to each application such as the macro languages used in Access or Excel

Script can also be used to write functions that are included in HTML pages to do tasks which can’t be done with HTML alone

An example of this is JavaScript

Which language to use depends on:

Organisational policy – your company may be ‘tied’ to Microsoft or Macintosh

Will it work on the hardware already used? Does it do what we need it to? Are current staff trained in its use? Is it reliable? Important for safety-critical

systems! Costs of developing and maintaining

programs Will it be expandable in future?