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# CSCE 145: Algorithmic Design I - PowerPoint PPT Presentation

CSCE 145: Algorithmic Design I. Chapter 1 Intro to Computers and Java Muhammad Nazmus Sakib. Computer Basics. Section 1.1. Computer Systems. Hardware The Physical Machine Software Set of programs Set of instructions. Hardware and Memory. Central Processing Unit (CPU)

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### CSCE 145: Algorithmic Design I

Chapter 1

Intro to Computers and Java

• Section 1.1

• Hardware

• The Physical Machine

• Software

• Set of programs

• Set of instructions

• Central Processing Unit (CPU)

• Also known as the Processor

• Device that performs the instructions in a program

• Example

• Intel Core i7

• Memory

• Holds data for the computer to process

• Two forms

• Main Memory

• Volatile

• Example - RAM

• Auxiliary Memory

• Non-volatile

• Example – Hard drive

• Bit = Binary Digit (0,1)

• Byte = groups of bits

• 1 Byte = 8 Bits

• Byte is the smallest addressable unit of memory

• Main memory consists of a long list of numbered bytes

• The number of a byte in memory is called an Address

• 1 byte is not large enough to store all kinds of data

• Data can be stored in several adjacent bytes

• These adjacent bytes are considered a single Memory Location

• Address of the Memory Location

• Address of the first byte

• File

• A group of bytes stored in auxiliary memory

• Directory

• Also known as Folder

• Contains groups of files

• A set of instructions

• A program that supervises a computer’s operation

• Examples

• Windows XP/7/8

• UNIX

• Linux, Ubuntu

• Mac OS X

• High Level Languages

• Java, C, C++, C#, Visual Basic, Python

• Low Level Languages

• Assembly Language

• Machine Language

• A Translator

• Translates from High Level Language to Low Level Language

• Source code -> Object Code

• Compile Once, Execute Often

• Translator + Executor

• Alternates between translation & execution

• Translates every time

• Interpreted programs are slower than compiled ones

Java Bytecode

• An intermediate language for Java

• A compiler translated Java code into Bytecode

• Java Virtual Machine (JVM)

• Translator to translate & execute Java Bytecode

• Bytecode runs in any computer that has JVM

• Portability

• Java program consists of Classes

• A piece of code

• Generally reside in one file

• Class loader connects the Classes

• Section 1.2

• Started in 1991

• James Gosling and his team

• Sun Microsystems

• Applications

• Regular programs

• Applets

• Little applications

• Sent over the Internet

• Section 1.3

• Objects

• Attributes

• States

• Behaviors

• Methods

• Captures the behavior

• Classes

• Blueprint for Objects

• Encapsulation

• Information Hiding

• Polymorphism

• Many forms

• Example – “Go play your favorite sport”

• Inheritance

• Way of organizing Classes

• Like a Recipe!

• A set of directions for solving a problem

• Often written in Pseudocode

• Combination of English & Programming Language

Pseudocode Example

• Algorithm to compute the total cost of a list of items

• Write the number o on the whiteboard.

• For each item on the list

• Add the cost of the item to the number on the whiteboard

• Replace the number on the whiteboard with the result of this addition.

• Announce that the answer is the number written on the whiteboard.

• Bug

• A mistake in a program

• Debugging

• Process of eliminating mistakes

• Syntax error

• Grammatical mistakes

• Run-time error

• Error during execution

• Logic error

• Conceptual mistakes in algorithm

• Java Class Library

• Java API

• Example

• System.out.println