CSCE 145: Algorithmic Design I

1. CSCE 145: Algorithmic Design I Chapter 1 Intro to Computers and Java Muhammad NazmusSakib

2. Computer Basics • Section 1.1

3. Computer Systems • Hardware • The Physical Machine • Software • Set of programs • Set of instructions

4. Hardware and Memory • Central Processing Unit (CPU) • Also known as the Processor • Device that performs the instructions in a program • Example • Intel Core i7

5. 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

6. 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

7. 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

8. Main Memory

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

10. Programs • A set of instructions

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

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

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

14. Interpreters • Translator + Executor • Alternates between translation & execution • Translates every time • Interpreted programs are slower than compiled ones

15. 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

16. Compiling & Running

17. 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

18. A Sip of Java • Section 1.2

19. History of Java • Started in 1991 • James Gosling and his team • Sun Microsystems

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

21. Programming Basics • Section 1.3

22. Object-Oriented Programming • Objects • Attributes • States • Behaviors • Methods • Captures the behavior • Classes • Blueprint for Objects

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

24. Inheritance

25. Algorithms • Like a Recipe! • A set of directions for solving a problem • Often written in Pseudocode • Combination of English & Programming Language

26. 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.

27. 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

28. Software Reuse • Java Class Library • Java API • Example • System.out.println