COMP 110COMP 110Computer BasicsComputer Basics

Luv KohliAugust 25, 2008

MWF 2-2:50 pmSitterson 014

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AnnouncementsAnnouncementsjGRASP

Office Hours◦Link to survey on web site

Honor Code document

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Questions?Questions?

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Today in COMP 110Today in COMP 110

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Hardware and MemoryPrograms and CompilingYour first program

Before ProgrammingBefore ProgrammingNeed to know basics of a

computer◦ If you drive a car you should

know it runs on gasolineWhat’s in the box?

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Hardware vs. SoftwareHardware vs. SoftwareHardware - physical machine

◦CPU, MemorySoftware - programs that give

instructions to the computer◦Windows XP, Games, jGRASP

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HardwareHardware

An aside: there is a computer museum in the first floor lobby of Sitterson Hall

Hardware Hardware CPU (Central Processing Unit) - the

“Brain”◦Executes your instructions◦GHz - number of instructions per second, how

fast is the computer◦Dual Core - multiple processing units per CPU,

multiple brains

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MemoryMemoryHolds data for the computerHow much the “Brain” can rememberMain Memory

◦Memory computer uses for intermediate calculations (program you are running)

◦ExpensiveAuxiliary Memory (Secondary Memory)

◦Disk drives, CDs, Flash drives◦Cheap

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RAM (random access memory)RAM (random access memory)Your main memoryRandom access?

◦Fast access◦Access any location in memory in constant

time

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Measuring memoryMeasuring memory2 gigabytes (GB) of RAM

◦Bytes - measurement of memory◦Megabyte (MB) = 1 million (106) bytes (or

1,048,576 = 220 bytes)◦Gigabyte (GB) = 1 billion (109) bytes (or

1,073,741,824 = 230 bytes)

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What is a byte?What is a byte?1 byte = 8 bits (thanks to Dr. Brooks)Bit = 0 or 1 (off or on)Language of the computer is bits 0 0 1 1 1 0 1 0 - 1 byte of 8 bits

Characters, numbers, encoded as series of bits – a byte:◦ 0: 00110000 ◦ A: 01000001◦ a: 01100001

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ProgramProgramSet of instructions for a CPU to follow

You will be writing programs◦We will look at one soon

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public class Hello{ public static void main(String[] args) { System.out.println("Hello world!"); }}

Programming LanguagesProgramming Languages

Your Program

Compiler

Machine Language (Bits)

High-level language (human readable)

Low-level language(computer readable)

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JavaJavaObject-oriented programming (OOP)

languageBased on the world

around us

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Objects, Methods, and Classes (oh my!)Objects, Methods, and Classes (oh my!)

Object – program construction that has data and methods

Methods – actions performed by objectsClass – a type of object (e.g. Vehicle, Television)

– objects in same class have same kinds of data and methods

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Class: Car Object: myCar

Data Make Honda

Model Civic

Methods Accelerate() Accelerate

Brake() Decelerate

Java: three main design principlesJava: three main design principles

Encapsulation

Polymorphism

Inheritance

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EncapsulationEncapsulationInformation hidingPackaging things up, only part of what is

going on is visible◦myCar.accelerate()◦yourCar.accelerate()

Just call these methods, the car will execute them

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PolymorphismPolymorphism“Many forms”One method call can cause different

actions in different contexts◦Class Airplane

Object: myAirplane.accelerateToMaxSpeed() 550mph

◦Class Car Object: myCar.accelerateToMaxSpeed() 100mph

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InheritanceInheritanceWay of organizing classesAt each level, classification becomes

more specific

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Vehicle

Automobile Bus

Family car Sports car School Bus Luxury Bus

Sample Java Program (section 1.3)Sample Java Program (section 1.3)

import java.util.*;public class FirstProgram{ public static void main(String[] args) { System.out.println("Hello out there."); System.out.println("I will add two numbers for you."); System.out.println("Enter two whole numbers on a line:");

int n1, n2;

Scanner keyboard = new Scanner(System.in); n1 = keyboard.nextInt(); n2 = keyboard.nextInt();

System.out.println("The sum of those two numbers is"); System.out.println(n1 + n2); }}

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java.util Packagejava.util Packageimport java.util.*;

Package = library of classes (standard programs)Different libraries have different classes and

functions◦ Physics library = Newtonian Physics◦ java.util.* = Java utility classes, used for many things

including reading data from keyboard

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Begin the programBegin the program

public class FirstProgram{ public static void main(String[] args) {

Begin a program named FirstProgramProgram names should make senseA program is also a class in Java

◦ A program class has a unique method ‘main’

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Output to screenOutput to screenSystem.out.println("Hello out there.");System.out.println("I will add two numbers for

you.");System.out.println("Enter two whole numbers on a

line:");

Write what is in quotes to screen

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Invoke methods on objectsInvoke methods on objects

myCar.start();

airplane.land();

System.out.println(“Hi”);

Object

Method

Invoke Method25

Arguments

VariableVariableint n1, n2;

Variable - store piece of datan1 - store integern2 - store integer

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Create Scanner ObjectCreate Scanner ObjectScanner keyboard = new Scanner(System.in);

Create object or instance (keyboard) of Scanner class

Car myCar = new Car();

Class Object Not always System.in

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Call method on objectCall method on object

n1 = keyboard.nextInt();

Read an integer from the keyboard and store it in n1

Object Method

Invoke/Call

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Output to screenOutput to screenSystem.out.println("The sum of those two numbers

is");

System.out.println(n1 + n2);

Add n1 and n2Print the sum to the screen

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Sample Java Program (section 1.3)Sample Java Program (section 1.3)

import java.util.*;public class FirstProgram{ public static void main(String[] args) { System.out.println("Hello out there."); System.out.println("I will add two numbers for you."); System.out.println("Enter two whole numbers on a line:");

int n1, n2;

Scanner keyboard = new Scanner(System.in); n1 = keyboard.nextInt(); n2 = keyboard.nextInt();

System.out.println("The sum of those two numbers is"); System.out.println(n1 + n2); }}

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WednesdayWednesdayDesigning Programs (Read 1.2)If time, start primitive types (start

reading 2.1)

Come to office hours if jGRASP is not working

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