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Chapter 1

Chapter 1. An Overview of Computers and Programming Languages. Chapter Objectives. Learn about different types of computers Explore the hardware and software components of a computer system Learn about the language of a computer Learn about the evolution of programming languages

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Chapter 1

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  1. Chapter 1 An Overview of Computers and Programming Languages

  2. Chapter Objectives • Learn about different types of computers • Explore the hardware and software components of a computer system • Learn about the language of a computer • Learn about the evolution of programming languages • Examine high-level programming languages

  3. Chapter Objectives • Discover what a compiler is and what it does • Examine how a Java program is processed • Learn what an algorithm is and explore problem-solving techniques • Become aware of structured and object-oriented programming design methodologies

  4. Introduction • Computers have greatly effected our daily lives – helping us complete many tasks • Computer programs (software) are designed specifically for each task • Software is created with programming languages • Java is an example of a programming language

  5. An Overview of the History of Computers • 1950s: Very large devices available to a select few • 1960s: Large corporations owned computers • 1970s: Computers get smaller and cheaper • 1990s: Computers get cheaper and faster and are found in most homes

  6. Elements of a Computer System • A computer has 2 components • Hardware • Software

  7. Hardware Components of a Computer • Central Processing Unit (CPU) • Main Memory

  8. Central Processing Unit • Control Unit (CU) • Arithmetic Logic Unit (ALU) • Program Counter (PC) • Instruction Register (IR) • Accumulator (ACC)

  9. Main Memory • Ordered sequence of cells (memory cells) • Directly connected to CPU • All programs must be brought into main memory before execution • When power is turned off, everything in main memory is lost

  10. Main Memory with 100 Storage Cells

  11. Secondary Storage • Provides permanent storage for information • Examples of secondary storage: • Hard Disks • Floppy Disks • ZIP Disks • CD-ROMs • Tapes

  12. Input Devices • Definition: devices that feed data and computer programs into computers • Examples: • Keyboard • Mouse • Secondary Storage

  13. Output Devices • Definition: devices that the computer uses to display results • Examples: • Printer • Monitor • Secondary Storage

  14. Hardware Components of a Computer

  15. Software • Software consists of programs written to perform specific tasks • Two types of programs • System Programs • Application Programs

  16. System Programs • System programscontrol the computer • The operating system is first to load when you turn on a computer

  17. Operating System (OS) • OS monitors overall activity of the computer and provides services • Example services: • memory management • input/output • activities • storage management

  18. Application Programs • Written using programming languages • Perform a specific task • Run by the OS • Example programs: • Word Processors • Spreadsheets • Games

  19. Language of a Computer • Machine language: the most basic language of a computer • A sequence of 0s and 1s • Every computer directly understands its own machine language • A bit is a binary digit, 0 or 1 • A byte is a sequence of eight bits

  20. Evolution of Programming Languages • Early computers programmed in machine language • Assembly languages were developed to make programmer’s job easier • In assembly language, an instruction is an easy-to-remember form called a mnemonic • Assembler: translates assembly language instructions into machine language

  21. Instructions in Assembly and Machine Language

  22. Evolution of Programming Languages • High-level languagesmake programming easier • Closer to spoken languages • Examples: • Basic • FORTRAN • COBOL • C/C++ • Java

  23. Evolution of Programming Languages • To run a Java program: • Java instructions need to be translated into an intermediate language called bytecode • Then the bytecode is interpreted into a particular machine language

  24. Evolution of Programming Languages • Compiler: A program that translates a program written in a high-level language into the equivalent machine language. (In the case of Java, this machine language is the bytecode.) • Java Virtual Machine (JVM) - hypothetical computer developed to make Java programs machine independent

  25. Processing a Java Program • Two types of Java programs: applications and applets • Source program: Written in a high-level language • Linker: Combines bytecode with other programs provided by the SDK and creates executable code • Loader: transfers executable code into main memory • Interpreter: reads and translates each bytecode instruction into machine language and then executes it

  26. Processing a Java Program

  27. Problem-Analysis-Coding-Execution Cycle • Algorithm: A step-by-step problem-solving process in which a solution is arrived at in a finite amount of time

  28. Problem-Solving Process • Analyze the problem: outline solution requirements and design an algorithm • Implement the algorithm in a programming language (Java) and verify that the algorithm works • Maintain the program: use and modify if the problem domain changes

  29. Problem-Analysis-Coding-Execution Cycle

  30. Programming Methodologies • Two basic approaches to programming design: • Structured design • Object-oriented design

  31. 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

  32. 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

  33. Example 1-1 Design an algorithm to find the perimeter and area of a rectangle. The perimeter and area of the rectangle are given by the following formulas: perimeter = 2 · (length + width) area = length · width

  34. The algorithm to find the perimeter and area of the rectangle is, therefore: 1. Get the length of the rectangle. 2. Get the width of the rectangle. 3. Find the perimeter using the following equation: perimeter = 2 · (length + width) 4. Find the area using the following equation: area = length · width

  35. Example 1-2 Design an algorithm that calculates the monthly paycheck of a sales-person at a local department store. Every salesperson has a base salary. The salesperson also receives a bonus at the end of each month based on the following criteria: If the salesperson has been with the store for five or less years, the bonus is $10 for each year that he or she has worked there. If the salesperson has been with the store for more than five years, the bonus is $20 for each year that he or she has worked there. The salesperson can earn an additional bonus as follows: If the total sale made by the salesperson for the month is more than $5000 but less than $10000, he or she receives a 3% commission on the sale. If the total sale made by the salesperson for the month is at least $10000, he or she receives a 6% commission on the sale.

  36. The algorithm to calculate a salesperson’s monthly paycheck. 1. Get baseSalary. 2. Get noOfServiceYears. 3. Compute the bonus by the following: if(noOfServiceYears is less than or equal to five) bonus = 10 · noOfServiceYears otherwise bonus = 20 · noOfServiceYears 4. Get totalSale.

  37. 5. Calculate additionalBonus using the following formula. if (totalSale is less than 5000) additionalBonus = 0 otherwise if(totalSale is greater than or equal to 5000 and totalSale is less than 10000) additionalBonus = totalSale · (0.03) otherwise additionalBonus = totalSale · (0.06) 6. Calculate payCheck using the equation payCheck = baseSalary + bonus + additionalBonus

  38. Chapter Summary • A computer system is made up of hardware and software components • Computers understand machine language; it is easiest for programmers to write in high-level languages • A compiler translates high-level language into machine language • High-level language steps to execute a program: edit, compile, link, load, and execute

  39. Chapter Summary • Algorithm: step-by-step problem-solving process in which a solution is arrived at in a finite amount of time • Three steps to problem solving: analyze the problem and design an algorithm, implement the algorithm in a programming language, and maintain the program • Two basic approaches to programming design: structured and object-oriented

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