INF120 Basics in JAVA Programming AUBG, COS dept

1. INF120 Basics in JAVA Programming AUBG, COS dept Lecture 01 Title: Computers, SDM, Algorithms, Programs and Java Malik Ch 1, Farrell Ch 1, Liang Ch 1

2. Lecture Contents: • Computers • Software Development Method • Algorithms • Programs • Java Prog Lan

3. What is a Computer? “A device for counting or computing “ A computer consists of a CPU, memory, hard disk, CD drive, monitor, printer, and communication devices.

4. CPU The central processing unit (CPU) is the brain of a computer. It retrieves instructions from memory and executes them. The CPU speed is measured in megahertz (MHz), with 1 megahertz equaling 1 million pulses per second. The speed of the CPU has been improved continuously. If you buy a PC now, you can get an Intel Pentium 4 Processor at 3 gigahertz (1 gigahertz is 1000 megahertz).

5. Memory Memory is to store data and program instructions for CPU to execute. A memory unit is an ordered sequence of bytes, each holds eight bits. A program and its data must be brought to memory before they can be executed. A memory byte is never empty, but its initial content may be meaningless to your program. The current content of a memory byte is lost whenever new information is placed in it.

6. How Data is Stored? Data of various kinds, such as numbers, characters, and strings, are encoded as a series of bits (zeros and ones). Computers use zeros and ones because digital devices have two stable states, which are referred to as zero and one by convention. The programmers need not to be concerned about the encoding and decoding of data, which is performed automatically by the system based on the encoding scheme. The encoding scheme varies. For example, character ‘J’ is represented by 01001010 in one byte. A small number such as three can be stored in a single byte. If computer needs to store a large number that cannot fit into a single byte, it uses a number of adjacent bytes. No two data can share or split a same byte. A byte is the minimum storage unit.

7. Language of a Computer (continued) Java Programming: From Problem Analysis to Program Design, 4e 7

8. Storage Devices Memory is volatile, because information is lost when the power is off. Programs and data are permanently stored on storage devices and are moved to memory when the computer actually uses them. There are three main types of storage devices:Disk drives (hard disks and floppy disks), CD drives (CD-R and CD-RW), and Tape drives.

9. Output Devices: Monitor The monitor displays information (text and graphics). The resolution and dot pitch determine the quality of the display.

10. Monitor Resolution and Dot Pitch resolution The screen resolution specifies the number of pixels in horizontal and vertical dimensions of the display device. Pixels (short for “picture elements”) are tiny dots that form an image on the screen. A common resolution for a 17-inch screen, for example, is 1,024 pixels wide and 768 pixels high. The resolution can be set manually. The higher the resolution, the sharper and clearer the image is. dot pitch The dot pitch is the amount of space between pixels, measured in millimeters. The smaller the dot pitch, the sharper the display.

11. Communication Devices A regular modem uses a phone line and can transfer data in a speed up to 56,000 bps (bits per second). A DSL (digital subscriber line) also uses a phone line and can transfer data in a speed 20 times faster than a regular modem. A cable modem uses the TV cable line maintained by the cable company. A cable modem is as fast as a DSL. Network interface card (NIC) is a device to connect a computer to a local area network (LAN). The LAN is commonly used in business, universities, and government organizations. A typical type of NIC, called 10BaseT, can transfer data at 10 mbps (million bits per second).

12. Programs Computer programs, known as software, are instructions to the computer. You tell a computer what to do through programs. Without programs, a computer is an empty machine, known as hardware. Computers do not understand human languages, so you need to use computer languages to communicate with them. Programs are written using programming languages.

13. Programming Languages Machine language is a set of primitive instructions built into every computer. The instructions are in the form of binary code, so you have to enter binary codes for various instructions.Program with native machine language is a tedious process. Moreover the programs are highly difficult to read and modify. For example, to add two numbers, you might write an instruction in binary like this: 1101101010011010 Machine Language Assembly Language High-Level Language

14. Programming Languages Assembly languages were developed to make programming easy. Since the computer cannot understand assembly language, however, a program called assembler is used to convert assembly language programs into machine code. For example, to add two numbers, you might write an instruction in assembly code like this: ADDF3 R1, R2, R3 Machine Language Assembly Language High-Level Language

15. Programming Languages The high-level languages are English-like and easy to learn and program. For example, the following is a high-level language statement that computes the area of a circle with radius 5: area = 5 * 5 * 3.1415; Machine Language Assembly Language High-Level Language

16. Popular High-Level Languages

17. Interpreting/Compiling Source Code A program written in a high-level language is called a source program or source code. Because a computer cannot understand a source program, a source program must be translated into machine code for execution. The translation can be done using another programming tool called an interpreter or a compiler.

18. Interpreting Source Code An interpreter reads one statement from the source code, translates it to the machine code or virtual machine code, and then executes it right away, as shown in the following figure. Note that a statement from the source code may be translated into several machine instructions.

19. Compiling Source Code A compiler translates the entire source code into a machine-code file, and the machine-code file is then executed, as shown in the following figure.

20. Operating Systems The operating system (OS) is a program that manages and controls a computer’s activities. The popular operating systems for general-purpose computers are Microsoft Windows, Mac OS, and Linux. Application programs, such as a Web browser or a word processor, cannot run unless an operating system is installed and running on the computer.

21. Problem Solving Process • Developing SW (computer programs) is not only a pure programming activity. • Developing SW (computer programs) is a sequence of sequential stages, known as • Problem Solving Process or • SDM • SLC • PDC

22. Problem-Solving Process Analyze the problem and outline the problem and its solution requirements Design an algorithm to solve the problem Implement the algorithm in a programming language, such as Java Verify that the algorithm works Maintain the program by using and improving it and modifying it if the problem domain changes Java Programming: From Problem Analysis to Program Design, 4e 22

23. Problem-Analysis-Coding-Execution Cycle Java Programming: From Problem Analysis to Program Design, 4e 23

24. Software Development Process

25. Requirement Specification A formal process that seeks to understand the problem and document in detail what the software system needs to do. This phase involves close interaction between users and designers. Most of the examples in this book are simple, and their requirements are clearly stated. In the real world, however, problems are not well defined. You need to study a problem carefully to identify its requirements.

26. System Analysis Seeks to analyze the business process in terms of data flow, and to identify the system’s input and output. Part of the analysis entails modeling the system’s behavior. The model is intended to capture the essential elements of the system and to define services to the system.

27. System Design The process of designing the system’s components. This phase involves the use of many levels of abstraction to decompose the problem into manageable components, identify classes and interfaces, and establish relationships among the classes and interfaces.

28. IPO The essence of system analysis and design is input, process, and output. This is called IPO.

29. Implementation The process of translating the system design into programs. Separate programs are written for each component and put to work together. This phase requires the use of a programming language like Java. The implementation involves coding, testing, and debugging.

30. Testing Ensures that the code meets the requirements specification and weeds out bugs. An independent team of software engineers not involved in the design and implementation of the project usually conducts such testing.

31. Deployment Deployment makes the project available for use. For a Java applet, this means installing it on a Web server; for a Java application, installing it on the client's computer.

32. Maintenance Maintenance is concerned with changing and improving the product. A software product must continue to perform and improve in a changing environment. This requires periodic upgrades of the product to fix newly discovered bugs and incorporate changes.

33. Programming Methodologies Two basic approaches to programming design Structured Design Object-Oriented Design Java Programming: From Problem Analysis to Program Design, 4e 33

34. Structured Design A problem is divided into smaller subproblems Each subproblem is solved The solutions of all subproblems are then combined to solve the problem Java Programming: From Problem Analysis to Program Design, 4e 34

35. Object-Oriented Design (OOD) In OOD, a program is a collection of interacting objects An object consists of data and operations Steps in OOD Identify objects Form the basis of the solution Determine how these objects interact Java Programming: From Problem Analysis to Program Design, 4e 35

36. Understanding Objects and Classes Objects Made up of attributes and methods Attributes Characteristics that define object Differentiate objects of same class Value of attributes is object’s state Class Describes objects with common properties Definition Instance Java Programming, Fifth Edition 36

37. Understanding Objects and Classes Java Programming, Fifth Edition 37

38. Object-Oriented Design Example 1 Problem statement Write a program to input the length and width of a rectangle, and calculate and print the perimeter and area of the rectangle Nouns Length, width, rectangle, perimeter, area Java Programming: From Problem Analysis to Program Design, 4e 38

39. class Rectangle with 2 Data Members and 7 Operations Java Programming: From Problem Analysis to Program Design, 4e 39

40. Object-Oriented Design Example 2 An inoperable candy machine has a cash register and four dispensers to hold and release items sold by the machine The machine sells: candies, chips, gum, and cookies Write a program for this candy machine so that it can be put into operation Java Programming: From Problem Analysis to Program Design, 4e 40

41. Object-Oriented Design Example 2 (continued) Java Programming: From Problem Analysis to Program Design, 4e 41

42. Object-Oriented Design Example 2 (continued) Java Programming: From Problem Analysis to Program Design, 4e 42

43. Algorithms • Computer programs implement algorithms. • So, what is an algorithm?

44. Algorithms definitions Definition 1: A step-by-step problem-solving process in which a solution is arrived at in a finite amount of time Definition 2: A procedure for solving a problem in terms of 1.   the actions to be executed, and 2.  the order in which these actions are to be executed is called an algorithm. Definition 3: An algorithm is a list of steps for solving a problem.

45. Classification of algorithms: • Linear or Sequence algorithms; • Branch algorithms; • Loop algorithms.

46. Design Notations Three “notations” used to document algorithms: •Flowchart also called control-flow diagram •Pseudo code Uses English-like phrases with some Java terms to outline the program •Hierarchy chart Show how the different parts of a program relate to each other

47. Problem: Converting Miles to Kilometers Describe the algorithm Converting miles to kilometers

48. Converting Miles to Kilometers:flowchart /control-flow diagram/

49. Converting Miles to Kilometers:using pseudo code Converting miles to kilometers 1. Read the number of miles 2. Set the number of kilometers to 1.609 * miles 3. Display the number of kilometers

50. Converting Miles to Kilometers:using hierarchy chart