UNIVERSITI TENAGA NASIONAL “Generates Professionals” CHAPTER 4 : Part 2 INTRODUCTION TO SOFTWARE DEVELOPMENT: PROGRAMMING & LANGUAGES

UNIVERSITI TENAGA NASIONAL “Generates Professionals” 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

UNIVERSITI TENAGA NASIONAL “Generates Professionals” 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

UNIVERSITI TENAGA NASIONAL “Generates Professionals” 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

UNIVERSITI TENAGA NASIONAL “Generates Professionals” 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

UNIVERSITI TENAGA NASIONAL “Generates Professionals” 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 Example: MOV AL, 61h ; Load AL with 97 decimal (61 hex)

UNIVERSITI TENAGA NASIONAL “Generates Professionals” 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

UNIVERSITI TENAGA NASIONAL “Generates Professionals” 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

UNIVERSITI TENAGA NASIONAL “Generates Professionals” 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

UNIVERSITI TENAGA NASIONAL “Generates Professionals” Major Programming Languages FORTRAN COBOL BASIC RPG Visual Basic C Java

UNIVERSITI TENAGA NASIONAL “Generates Professionals” FORTRAN The first high-level language Stands for FORmula TRANslator Used primarily for engineering, mathematical, and scientific tasks

UNIVERSITI TENAGA NASIONAL “Generates Professionals” COBOL Stands for COmmon Business-Oriented Language Used primarily for business requirements –Processes large data files –Produces well-formatted reports

UNIVERSITI TENAGA NASIONAL “Generates Professionals” 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

UNIVERSITI TENAGA NASIONAL “Generates Professionals” RPG Stands for Report Program Generator Designed to allow rapid creation of reports –Programmer simply describes the source data and desired report format

UNIVERSITI TENAGA NASIONAL “Generates Professionals” 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

UNIVERSITI TENAGA NASIONAL “Generates Professionals” 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 #include main() { int number; printf("Enter an integer\n"); scanf("%d",&number); printf("Integer entered by you is %d\n", number); return 0; }

UNIVERSITI TENAGA NASIONAL “Generates Professionals” 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 public class HelloWorld { // method main(): ALWAYS the APPLICATION entry point public static void main (String[] args) { System.out.println ("Hello World!"); }

UNIVERSITI TENAGA NASIONAL “Generates Professionals” 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

UNIVERSITI TENAGA NASIONAL “Generates Professionals” 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

UNIVERSITI TENAGA NASIONAL “Generates Professionals” 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

UNIVERSITI TENAGA NASIONAL “Generates Professionals” Object-Oriented Languages C++ Java C# Visual Basic

UNIVERSITI TENAGA NASIONAL “Generates Professionals” 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

UNIVERSITI TENAGA NASIONAL “Generates Professionals” 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

UNIVERSITI TENAGA NASIONAL “Generates Professionals” 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

UNIVERSITI TENAGA NASIONAL “Generates Professionals” 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