Computer Hardware and Software Introduction

1. Computer Hardware and Software Introduction Mr. Smith AP Computer Science A

3. History of Computers Abacus – 1100 BC Slide rule - 1617Mechanical calculator - 1642Automatic loom (punched cards) - 1804 Babbage’s computer – 1830sBoolean logic – 1850s Hollerith’s electric tabulator - 1880Analog computer – 1927EDVAC – 1946ENIAC - 1947 Transistor - 1947 Integrated circuit – late 1950sUNIVAC – 1951Microprocessor – 1971Altair 8880 – 1975Apple II – 1977IBM PC – 1981World Wide Web – 1990s

4. What is Programming? • A computer must be programmed to perform a task • A computer is a machine that: • Stores data (numbers, words, and pictures) • Interacts with devices (monitor, sound system, printer) • Executes programs • Typical operations are: • Put a red dot onto this screen position • Send letter Z to the printer • Get a number from a specific location in memory • Multiply two numbers • If this value > 10, execute a certain instruction • A computer program tells the computer, in much detail, the sequence of steps to complete a task.

5. Anatomy of a Computer Central Processing Unit (CPU): • It is the Brain of your computer. It consists of a single chip (integrated circuit) or a small number of chips • A computer chip has plastic or metal housing, metal connectors, and inside wiring made mainly of silicon • A chip contains millions of transistors (the elements that enable electrical signals to control other electrical signals) • The main tasks of the CPU are: • To locate and execute the program instructions • To carry out arithmetic operations • To fetch data from storage and input/output devices • To send data back to devices

6. Anatomy of a Computer Storage: • Primary – known as RAM or Memory • Fast, but relatively expensive • Made from memory chips • Loses its data when power is turned off • Secondary – usually a hard disk • Less expensive storage • Keeps data when electricity is turned off • CD-ROM • Flash drive • DVD

7. Anatomy of a Computer Other things to know about your computer: • I/O Devices • Enables you to interact with a computer • Keyboard, mouse, monitors, printers • Motherboard • Contains CPU, RAM, and connectors to peripheral devices • Bus • Set of electrical lines that connect the CPU, RAM, and connectors • Network • Allows a computer to communicate with other computers or devices not directly connected to this computer

8. Translating Programs to Machine Code • A Compiler translates high level language (Java program code) into machine code (also known as Java bytecode) • An Interpreter is similar to a compiler but translates and executes a single statement at a time. • An Editor is used to create or change a Java program • The Editor and Compiler may be part of the same software known as an Integrated Development Environment (IDE), such as eclipse. An IDE can also contain a Debugger. • A Java Virtual Machine (JVM) is written for every major operating system. It is like a simulated CPU that runs inside an operating system. The JVM reads the bytecode and executes the program. • The Operating system manages the computer resources

9. Compiling a Simple Program Printing to the console: public class TrivialProgram { public static void main (String[] args) { System.out.print(“This prints a line. ”); System.out.println(“This stays on the same line.”); System.out.println(“This prints on a new line.”); } } This program will print the following to the console: This prints a line. This stays on the same line. This prints on a new line. Whenever you call a method in Java, you need to specify these 3 items Object Method Parameters (out object in System class)

10. JavaConceptsCh1Homework • This assignment will give you practice printing to the console. You need to use System.out.print() and System.out.println() methods. We are also using static methods in this assignment. • In eclipse, create a new project named JavaConcepts. On the first screen, make sure that all the radio buttons are active on the top options. This project has no additional jar files you need to use. • Create a new package named javaconcepts in this project. • Download the JavaConceptsCh1.java and JavaConceptsCh1Tester.java classes and put them in this new package. Pay careful attention to the comments for instructions and explanations. • Ex.R1.2, R1.4, R1.7, R1.12 (page 28) – create answersToReviewExercises() methodto print your answers to the console. • Ex. P1.2 (page 29) – create facePrinter() method to print a face using text characters. Be creative. • Ex.P1.3 (page 29) – create ticTacToeBoard() method – must use looping to get full credit; this is an example of a fence post problem.

11. Java Comments Using comments in your Java programs: • Single line comments – use // • Anything following // on the same line is a comment • Robot.move(); // This makes the robot move • Multi-line comments – use /* and */ • Anything after the /* and before the */ is a comment • Comments can span lines • /* The following while loop will calculate the interest payment for my house */ • Javadoc comments – use /** and */ • Anything after the /** and before the */ is a comment • Comments can span lines • /** This program is used to create a robot that can go through a maze */

12. Java Errors Errors encountered within Java programs: • Compile-time errors • Violation of the rules of the programming language • Compiler detects syntax/lexical errors • Examples: Missing semi-colons, missing brackets, and missing parentheses are examples of syntax errors. Misspelling a method name is an example of a lexical error caught at compile-time. • Logic errors • Causes the program to take an action that the programmer did not intend. • Program runs without an error message.

13. Java Compilation Process How compilation works: • You type a Java source program into an IDE such as eclipse. The source code has the extension .java • The Compiler reads the source program and if it finds errors, it displays errors in the editor’s console. • After errors are corrected, the compiler is able to translate your source program into a class file (Java bytecode). This file has the extension .class • The Java Virtual Machine then does the following: • Loads the instructions for the program (.class file) • Starts the program • Loads any other necessary library (jar) files • JVM is the reason that we can run the program on different operating systems.

14. Java Compilation Process This is the result of saving your program in eclipse with no errors Class files Editor Compiler JVM Bytecode file ( .class file ) Source file ( .java file ) Running program Library files An Editor is used to create or modify source code A Compiler converts the source file into a Bytecode file This is the result of running your program in eclipse Jar files and System library files ( .jar file ) Eclipse is an IDE which is both an editor and compiler

15. Compiling a Simple Program Displaying a message in a dialog box: import javax.swing.JOptionPane; public class DialogBox { public static void main (String[] args) { JOptionPane.showMessageDialog(null, "Hello, World!"); System.exit(0); } } This program will display a message box: Hello, World! Press OK to acknowledge the message Class Package Parameters Parent Message Class This method brings up a confirmation dialog box that displays a message and waits for user to confirm it. Exits the program. A non-zero status indicates abnormal termination Check out Appendix C for list of Java Libraries

16. Compiling a Simple Program Using a dialog box to prompt for information: publicclass DialogViewer { publicstaticvoid main (String[] args) { String name = JOptionPane.showInputDialog("What is your name?"); System.out.print(name); System.exit(0); } } will display a dialog box that asks: What is your name? You would then enter your name and press Ok. Whatever you entered would be assigned to the name variable Parameter Prompt User input is assigned to this variable This method brings up an input dialog box which displays a prompt and waits for user to enter data into it

17. PrintAddress class PrintAddress class: Prompt the user to enter the following information in six separate dialog boxes:1) first name2) last name3) street address4) city5) state6) zipThen print this information to the console in the following format:John Doe110 Oak StreetWinston-Salem, NC 27101At the end, display the following dialog message: Thank you for entering your name and address