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) ▫Also known as the Processor ▫Device that performs the instructions in a program ▫Example  Intel Core i7

Hardware and Memory Memory ▫Holds data for the computer to process ▫Two forms  Main Memory  Volatile  Example - RAM  Auxiliary Memory  Non-volatile  Example – Hard drive

Bits, Bytes & Address Bit = Binary Digit (0,1) Byte = groups of bits ▫1 Byte = 8 Bits ▫Byte is the smallest addressable unit of memory Address ▫Main memory consists of a long list of numbered bytes ▫The number of a byte in memory is called an Address

Memory Locations 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

Main Memory

Files & Directories File ▫A group of bytes stored in auxiliary memory Directory ▫Also known as Folder ▫Contains groups of files

Programs A set of instructions

Operating Systems A program that supervises a computer’s operation Examples ▫Windows XP/7/8 ▫UNIX ▫Linux, Ubuntu ▫Mac OS X

Programming Languages High Level Languages ▫Java, C, C++, C#, Visual Basic, Python Low Level Languages ▫Assembly Language ▫Machine Language

Compilers A Translator Translates from High Level Language to Low Level Language Source code -> Object Code Compile Once, Execute Often

Interpreters 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

Compiling & Running

Class Loader Java program consists of Classes ▫A piece of code ▫Generally reside in one file Class loader connects the Classes ▫Similar to a Linker

A Sip of Java Section 1.2

History of Java Started in 1991 James Gosling and his team ▫Sun Microsystems

Applications & Applets Applications ▫Regular programs ▫Runs in your computer Applets ▫Little applications ▫Runs in your web browser ▫Sent over the Internet

Programming Basics Section 1.3

Object-Oriented Programming Objects ▫Attributes ▫States ▫Behaviors Methods ▫Captures the behavior Classes ▫Blueprint for Objects

Object-Oriented Programming Encapsulation ▫Information Hiding Polymorphism ▫Many forms ▫Example – “Go play your favorite sport” Inheritance ▫Way of organizing Classes

Inheritance

Algorithms 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.

Testing & Debugging 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

Software Reuse Java Class Library ▫Java API Example ▫System.out.println