Module 4 Part 2 Introduction To Software Development : Programming & Languages Introduction To Software Development : Programming & Languages

Module Objectives At the end of the module, students should be able to: –List and describe the levels of programming languages: machine, assembly, high level, very high level, and natural –Describe the major programming languages that are in use today –Explain the concepts of object-oriented programming

What is Programming ? Computer program –a series of instructions that directs a computer to perform task. Programming language –a set of words, symbols, and codes that enables a programmer to communicate instructions to a computer. –a set of rules that provides a way of telling the computer what operations to perform

Levels of Programming Languages Lower-level languages – more like the 0s and 1s the computer itself uses Higher-level languages – more like the languages people use Divided into five generations 1.Machine language 2.Assembly languages 3.High-level languages 4.Very high-level languages 5.Natural languages

1. Machine Language Programs and memory locations are written in strings of 0s and 1s Problems with machine languages –Programs are difficult to write and debug –Each computer has its own machine language Only option available to early programmers

2. Assembly Languages Substitute mnemonic codes for 0s and 1s –For example, A for add, C for compare, etc. –Use names rather than binary addresses for memory locations Require an assembler to translate the program into machine language Still used for programming chips and writing utility programs

3. High-Level Languages Transformed programming –Programmers could focus on solving problems rather than manipulating hardware –Programs could be written and debugged much more quickly Requires a compiler to convert the statements into machine language –Each computer has its own version of a compiler for each language

4. Very High-Level Languages Also called fourth-generation languages (4GLs) Considered nonprocedural languages –The programmer specifies the desired results, and the language develops the solution –Programmers can be about 10 times more productive using a fourth-generation language than a third-generation language

5. Natural Languages Resemble written or spoken English –Programs can be written in a natural syntax, rather than in the syntax rules of a programming language The language translates the instructions into code the computer can execute

Major Programming Languages FORTRAN COBOL BASIC RPG Visual Basic C Java

FORTRAN The first high-level language Stands for FORmula TRANslator Used primarily for engineering, mathematical, and scientific tasks

COBOL Stands for COmmon Business-Oriented Language Used primarily for business requirements –Processes large data files –Produces well-formatted reports

BASIC Stands for Beginners’ All- Purpose Symbolic Instruction Code Developed to teach programming to college students Became very popular with the introduction of the microcomputer

RPG Stands for Report Program Generator Designed to allow rapid creation of reports –Programmer simply describes the source data and desired report format

Visual Basic Allows programmer to create Windows-like user interfaces –Programmer drags a control (button, text box, etc.) onto the form –VB creates the code associated with that control VB is event-driven –The user controls the program

C C Originally designed to write systems software –Offers the ease of use of a high-level language with the efficiency of an assembly language Very portable – can be used with virtually every combination of computer and operating system

Java A network-friendly programming language that permits a piece of software to run directly on many different platforms –Allows programmers to write one version of the program, rather than a separate version of each platform Very useful for Internet development –Java applets can run in the user’s Web browser

Object-Oriented Programming Object – a self-contained unit that contains both data and its related functions Key terms in object-oriented programming –Encapsulation – an object isolates both its data and its related instructions –Attributes – facts that describe the object Also called properties –Methods – instructions that tell the object to do something –Messages – an outside stimulus that results in the change of the state of an object

Using Objects Programmers define classes of objects –The class contains all attributes that are unique to objects of that class –An object is an instance (occurrence) of a class Objects are arranged hierarchically in classes and subclasses –Subclasses are derived from classes –Inheritance – a subclass possesses all attributes of the class from which it is derived –Additional attributes can be coded in the subclasses

Activating the Object A message is sent to the object, telling it to do something –The object’s methods tell it how to do it Polymorphism – each object has its own way to process the message –For example, the class may have a Move method, but each subclass implements that method differently

Object-Oriented Languages C++ Java C# Visual Basic

C++ An enhancement of the C language –Includes all features of C –Adds support for object-oriented programming Can be used as simply an improvement of C, without the object-oriented features

Java A pure object-oriented program Used to create small programs called applets –Applets can be delivered over the Web and run on any platform

C# Microsoft’s answer to Java Has the same advantages over C++ that Java has Designed to work within Microsoft’s.NET environment –.NET is designed for building, deploying, and running Web-based applications

Visual Basic Previous versions supported some object technology The current version, VB.NET, is the first to support inheritance and polymorphism –These two traits are required for a true object- oriented language