King Fahd University of Petroleum & Minerals College of Computer Science & Engineering

King Fahd University of Petroleum & MineralsCollege of Computer Science & Engineering

Information & Computer Science Department

Lecture 1 : Introduction

ICS102 - Introduction to computing

ICS102: Intro To Comp2

Components of a Personal Computer

Questions :

- what are the input devices ?

- what are the output devices ?

http://upload.wikimedia.org/wikipedia/commons/4/41/Personal_computer%2C_exploded_5.svg


A motherboard, provides the electrical connections by which the other components of the system communicate and hosts the central processing unit as well as other subsystems and devices.

Motherboard


Motherboard example : Acer E360

http://upload.wikimedia.org/wikipedia/commons/9/9d/Acer_E360_Socket_939_motherboard_by_Foxconn.svg


CPU (Central Processing Unit)

The Central Processing Unit (CPU) or processor is the portion of a computer system that carries out the instructions of a computer program and is the primary element carrying out the computer's functions.

In an addition operation, the arithmetic logic unit (ALU) will be connected to a set of inputs and a set of outputs. The inputs provide the numbers to be added, and the outputs will contain the final sum.

Example: (3 + 2) = 5

3

2

5


• CPU memory

– Registers

– Cache

• Main memory (RAM):

– Data has to be in main memory so that CPU can access it

– Volatile: lost when program exits; computer shuts off

• Hard Disk, CD, etc.

– Persistent

– This is where you keep the data for long-term storage

Memory

Memory refers to computer components, devices, and recording media that hold digital data used for computing for some interval of time.

There are mainly three types of memory :


Main Memory…

10021003

1004

1005

CellAddress

Memory is divided intoMany memory locations (cells)

Each memory cell has a numeric address, which uniquely identifies it

Each cell contains a datavalue, e.g. 22


Main Memory…


The word “Hello.” stored in 6 memory cells

Main Memory…


Memory units : Bits and Bytes

• Bit -- most basic unit of memory

– 1 or 0, on or off

• 1 Byte = 8 bits

• In a computer, data values are stored as a sequence of bits

2

7

1004

1005

00000010

00000111

1004

1005


Program / CPU / Memory Interaction

• Example:

– Input read a number from keyboard

– Add 1 to it

– Output it on screen

KeyboardRAM

11 CPU

RAM

2 Monitor1 2 2

What is programming?


What is a program?

• A (software) program is a list of instructions intended to a computer

• The list must be ordered correctly

• A program has inputs and outputs

• Each instruction tells the computer to do something (an action, a calculation, a comparison)


Program Execution

• A program tells the CPU how to manipulate and/or move information

• Programming is about processing information

– Take some input, manipulate it in some way, and produce a particular output

ManipulationInputs Outputs

Program


Example 1 : Recipe for Scrambled Eggs

• Ingredients (Inputs) : two eggs, tablespoon of oil, salt

• Instructions (program):

– Add oil to pan

– Heat pan on stove

– Crack eggs into pan

– Add salt

– Mix until light and flakey

• Output: scrambled eggs


Example 2 : Currency Exchange

• Input:– Amount– Source Currency– Desired Currency

• Instructions– Look up in table current exchange rate for the selected

currencies– Calculate result as amount * exchange rate

• Output: result

Task : convert an amount of money in some currency (e.g. US Dollars) to another one (e.g. Saudi Riyals).


Programming language

• A programming language is the language used to write programs

• A programming language employs a set of rules that dictate how the words and symbols can be put together to form valid program statements

• A programming language has a syntax and semantics

• There are several types of languages (functional, Object-Oriented, etc.)

• In this course we focus on Java programming language.


Java

• Java is a programming language originally developed by James Gosling at Sun Microsystems

• It was first released in 1995.

• The language derives much of its syntax from C and C++.

• But has a simpler object model and fewer low-level facilities than C and C++.

http://upload.wikimedia.org/wikipedia/en/3/39/Java_logo.svg

http://en.wikipedia.org/wiki/File:James_Gosling_2005.jpg


Why Java?

Currently, Java is the most popular language in the world !


Why Java?

1. Simple

• Get started quickly

2. Concise

• Write less code

3. Object-oriented

• Better quality code

4. Portable

• Architecture neutral (write once run anywhere)

5. Secure

• More appropriate for Internet


Portability of Java

Classical model:

Java model:


Portability of Java

Write once, run anywhere: Because applications written in the Java programming language are compiled into machine-independent bytecodes, they run consistently on any Java platform.


A Java Program

• A Java program consists of one or more classes

• A Java class consists of one or more methods

• A Java method consists of one or more statements

A Java Program

Javaclasses

JavaMethods


A Java Program

• A Java program resides in one or more files.

• The file name of a Java program has extension .java.

• One of the classes of a Java program is called the driver class.

• The name of the driver class must be the same as the name of its Java file. (Java is case sensitive. So EX1 is different from ex1.)

• The diver class must contain a method called main. The execution of Java program starts from the main method of the driver class.


Example of a Java Program



Class nameMain method

Instruction

Class body



Also notice:

Curly braces } {



Also notice:

Parentheses ( )

Curly braces } {



Also notice:

Parentheses ( )

Curly braces } { Square brackets] [



Also notice:

A pair of braces } { define a block


Compiling and running a program

• Type in your program

• Save the program

– Store all your files in one directory for now

– Give the program the same name as the class

• Compile the program

– this produces a .class file

– Translates the program into something the computer can understand and execute (Java bytecode)

• Run the program

• Observe the result and adjust the program if necessary


Edit

Text Editor

Public class/*

Adventure.java

Public class Adven/* This program is an Arit*/

public static void main /* Program statements g System.out.print(“Wel }}


Compile - With Errors

Adventure.java


public static void main /* Program statements g System.print(“Welcome }}

Compiler

Errors and Warnings-------------------Error : The method print(String) is undefined forType System


Compile - Success

Adventure.java


public static void main /* Program statements g System.out.print(“Wel }}

Compiler

Adventure.class

00101101000101110110110100010111011101010001011101110101101000101110111010110100010111011101011010001011101110101101000101110111000101110111010110100010111011100101110111010110100010111011100101110111010110100010111011100101110111010110100010111011100101110111010110100010111011100101110


Run Program

Welcome to the ArithmThe date is Monday SepWhat is your name?FredWell Fred, after a dayThe cube appears to beYou find a Green door,The door closes behindThere is a feel of mat

Adventure

Fred

1

King Fahd University of Petroleum & Minerals College of Computer Science & Engineering

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