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

Transcription

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

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3 History of Computers Abacus 1100 BC Slide rule Mechanical calculator Automatic loom (punched cards) Babbage s computer 1830s Boolean logic 1850s Hollerith s electric tabulator Analog computer 1927 EDVAC 1946 ENIAC Transistor Integrated circuit late 1950s UNIVAC 1951 Microprocessor 1971 Altair Apple II 1977 IBM PC 1981 World 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 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. ); Object Method Parameters (out is a static PrintStream object in System class) 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 this method in Java, you need to specify these 3 items

9 System.out.println() public class System { public static PrintStream out; public class PrintStream { public void println(string s) {. public void print(string s) {.

10 JavaConceptsCh1 Homework 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() method to 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 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

14 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.

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

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

17 Compiling a Simple Program Using a dialog box to prompt for information: public class DialogViewer { public static void main (String[] args) { User input is assigned to this variable 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. Parameter Prompt This method brings up an input dialog box which displays a prompt and waits for user to enter data into it Whatever you entered would be assigned to the name variable

18 PrintAddress class PrintAddress class: Prompt the user to enter the following information in six separate dialog boxes: 1) first name 2) last name 3) street address 4) city 5) state 6) zip Then print this information to the console in the following format: John Doe 110 Oak Street Winston-Salem, NC At the end, display the following dialog message: Thank you for entering your name and address