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COMP 14 Introduction to Programming

COMP 14 Introduction to Programming. Adrian Ilie June 24, 2005. …from Last Time. Homework 1 due at midnight Fill in form with personal info Getting started with jGRASP Compile and Run test programs Any problems? Disable test for new versions. Today (ch. 1). Parts of the computer

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COMP 14 Introduction to Programming

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  1. COMP 14Introduction to Programming Adrian Ilie June 24, 2005

  2. …from Last Time • Homework 1 due at midnight • Fill in form with personal info • Getting started with jGRASP • Compile and Run test programs • Any problems? • Disable test for new versions

  3. Today (ch. 1) • Parts of the computer • hardware vs. software • CPU and memory • Binary numbers • What is an algorithm?

  4. Reading Check-Up hardware ________- computer components including the CPU, main memory, I/O devices, and secondary storage ________ - the brain of the computer, containing the CU, PC, IR, ALU, and ACC ________ - computer instructions to solve a problem The digits 0 and 1 are called _________ or the shortened term ________ CPU program binary digits bits

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

  6. Hardware vs. Software A computer is made up of hardware and software Software Hardware • CPU • ex: 2 GHz Pentium IV • input/output • keyboard • monitor • network card • main memory • ex: 256 MB RAM • secondary memory • ex: 20 GB hard drive • operating systems • Windows XP • Mac OS X • applications • games • Microsoft Word • Internet Explorer

  7. Hardware Organization CPU memory motherboard hard drive

  8. Central Processing Unit • Control Unit (CU) • "the brain" of the CPU • Program Counter (PC) • points to the next instruction to be executed • Instruction Register (IR) • holds the currently executing instruction • Arithmetic Logic Unit (ALU) • carries out all arithmetic and logical ops • Accumulator (ACC) • holds the results of the operations performed by the ALU

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

  10. Main MemoryWith 100 Cells Each memory cell has a numeric address, which uniquely identifies it

  11. CPU and Main Memory All programs must be brought into main memory before execution Chip that executes program instructions (processor) Primary storage area for programs and data that are in active use (RAM)

  12. Secondary Storage • Provides permanent storage for information • Retains information even when power is off • Examples of secondary storage: • Hard Disks • Floppy Disks • ZIP Disks • CD-ROMs • Tapes

  13. Secondary Storage Secondary memory devices provide long-term storage Information is moved between main memory and secondary memory as needed

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

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

  16. Input/Output Devices I/O devices facilitateuser interaction

  17. Hardware Components

  18. Opening MS Word • Use the mouse to select MS Word • The CPU requests the MS Word application • MS Word is loaded from the hard drive to main memory • The CPU reads instructions from main memory and executes them one at a time • MS Word is displayed on your monitor

  19. Questions ____________- points to the next instruction to be executed ____- a unique location in memory ____________- stores information permanently Instructions executed by the CPU must be first loaded to ________ program counter (PC) address secondary storage main memory

  20. Software Categories • Operating System • controls all machine activities • provides the user interface to the computer • first program to load when a computer is turned on • manages computer resources, such as the CPU, memory, and hard drive • examples: Windows XP, Linux, Mac OS X • Application • generic term for any other kind of software • examples: word processors, missile control systems, games

  21. Operating System (OS) • OS monitors overall activity of the computer and provides services • Written using programming language • Example services: • memory management • input/output • storage management

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

  23. Questions Classify the following pieces of software as operating system or application: • Microsoft Windows 2000 • Microsoft PowerPoint • Linux • Your COMP 14 programs OS app OS app

  24. It’s All About Data • Software is data • numbers, characters • instructions, programs • Hardware stores and processes data • read, write • add, subtract, multiply, divide

  25. Analog vs. Digital • Analog • continuous wave forms • ex: sound, music on an audio tape • Digital • the information is broken down into pieces, and each piece is represented separately • is ultimately represented as series of 0s and 1s for low voltage and high voltage • can be copied exactly • ex: music on a compact disc

  26. Representing Text Digitally • All information in a computer is digitized, broken down and represented as numbers. H i , H e a t h e r . 72 105 44 32 72 101 97 116 104 101 114 46 Corresponding upper and lower case letters are separate characters.

  27. Language of a Computer • Machine language: the most basic language of a computer • A sequence of 0s and 1s • binary digit, or bit • sequence of 8 bits is called a byte • Every computer directly understands its own machine language • why can't Windows programs run on Apple computers?

  28. 1 bit 2 bits 3 bits 4 bits 0 1 00 01 10 11 000 001 010 011 100 101 110 111 0000 0001 0010 0011 0100 0101 0110 0111 1000 1001 1010 1011 1100 1101 1110 1111 Bit Permutations Each additional bit doubles the number of possible permutations

  29. 1 bit ? 2 bits ? 3 bits ? 4 bits ? 5 bits ? How many items can be represented by Bit Permutations • Each permutation can represent a particular item • There are 2N permutations of N bits • N bits are needed to represent 2N unique items 21 = 2 items 22 = 4 items 23 = 8 items 24 = 16 items 25 = 32 items

  30. Binary Numbers • N bits to represent 2N values • N bits represent values 0 to 2N-1 • Example: 5 bits • 32 unique values (0-31) • 000002 = 010 • 111112 = 3110 24 23 22 21 20 16 + 8 + 4 + 2 + 1 = 31

  31. Converting Decimal to Binary • Let’s convert 114 to binary • Repeatedly divide by 2 and write down the remainder: 114/2=57 remainder 0 57/2=28 remainder 1 28/2=14 remainder 0 14/2=7 remainder 0 7/2=3 remainder 1 3/2=1 remainder 1 1/2=0 remainder 1 • Write the remainders in reverse order: 11100102=11410 • Proof – rewrite and add the equations above: 114=(((((((1*2)+1)*2+1)*2+0)*2+0)*2+1)*2+0)= =1*26+1*25+1*24+0*23+0*22+1*21+0*20

  32. Questions: Binary Numbers • What’s the maximum value a 6-bit number can represent? • What’s the decimal representation of 111010? • What’s the binary representation of 35? 26-1=63 25*1+24*1+23*1+22*0+21*1+20*0=58 3510=1000112

  33. Storage Capacity • Every memory device has a storage capacity, indicating the number of bytes (8 bits) it can hold • Various units: Unit Symbol Number of Bytes KB 210 = 1024 kilobyte megabyte gigabyte terabyte MB 220 (over 1 million) GB 230 (over 1 billion) TB 240 (over 1 trillion)

  34. Machine Language • Early computers programmed in machine language (only 0s and 1s) • Assembly languages were developed to make programmer’s job easier • Assembler: translates assembly language instructions into machine language

  35. Assembly and Machine Language

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

  37. Java and Machine Language To run a Java program: • Java instructions need to be translated into an intermediate language called bytecode. • The bytecode is interpreted into a particular machine language.

  38. Compiler • 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): A hypothetical computer developed to make Java programs machine independent.

  39. A Java Program public class ASimpleJavaProgram { public static void main(String[] args) { System.out.println("My first Java program."); System.out.println("The sum of 2 and 3 = " + 5); System.out.println("7 + 8 = " + (7 + 8)); } } Sample Run: My first Java program. The sum of 2 and 3 = 5 7 + 8 = 15

  40. Processing a Java Program • Program:written in Java using the Editor and compiled to Bytecode using the Compiler. • Loader: transfers the compiled code (bytecode) into main memory and loads the necessary Libraries. • Interpreter: reads and translates each bytecode instruction into machine language and then executes it.

  41. Problem Solving • The purpose of writing a program is to solve a problem • The general steps in problem solving are: • understand the problem • dissect the problem into manageable pieces • design a solution • consider alternatives to the solution and refine it • implement the solution • test the solution and fix any problems that exist

  42. Algorithm • Sequence of instructions used to carry out a task or solve a problem • May be written in either English or pseudocode • outline of a program that could be translated into actual code • May need refinement as you work Always write out your algorithm before you begin programming

  43. Problem-Analysis-Coding-Execution most important step without computer with computer

  44. Algorithm Design Example Problem: Convert change in cents to number of half-dollars, quarters, dimes, nickels, and pennies to be returned. Example: • given 646 cents • number of half-dollars: divide 646 by 50 • quotient is 12 (number of half-dollars) • remainder is 46 (change left over) • number of quarters: divide 46 by 25 • quotient is 1 (number of quarters) • remainder is 21 (change left over) • number of dimes, nickels, pennies • result: 12 half-dollars, 1 quarter, 2 dimes, 0 nickels, 1 penny

  45. Resulting Algorithm • Get the change in cents • Find the number of half-dollars • Calculate the remaining change • Find the number of quarters • Calculate the remaining change • Find the number of dimes • Calculate the remaining change • Find the number of nickels • Calculate the remaining change • The remaining change is the number of pennies.

  46. Exercise • Execution of c=2*a+b in a computer

  47. To do • Read ch. 2 • Exercise 10 in ch. 1 (algorithm design)

  48. What’s Ahead... • Java Basics • Homework 1 due tonight • Homework 2 assigned Monday • Quiz Tuesday: computers and Java basics

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