Lecture Outline
- What Is a Computer?
- Computer Organization
- Evolution of Operating Systems
- Personal, Distributed and Client/Server Computing
- Machine Languages, Assembly Languages and High-Level Languages
- History of C++
- History of Java
- Java Class Libraries
- FORTRAN, COBOL, Pascal and •Ada - BASIC, Visual Basic, Visual C++, C# and .NET
- The Internet and the World Wide Web
- Basics of a Typical Java Environment
- Thinking About Objects: Introduction to Object Technology and the Unified Modeling Language
- Discovering Design Patterns: Introduction
What is a Computer?
Computers:
- Performs computations and makes logical decisions
- Millions / billions times faster than human beings
Computer programs:
- Sets of instructions for which computer processes data
Hardware
- Physical devices of computer system
Software
- Programs that run on computers
Computer Organization
•Six logical units of computer system
1– Input unit
• Mouse, keyboard
2– Output unit
• Printer, monitor, audio speakers
3– Memory unit
• Retains input and processed information
4– Arithmetic and logic unit (ALU)
• Performs calculations
5– Central processing unit (CPU)
• Supervises operation of other devices
6– Secondary storage unit
• Hard drives, floppy drives
Evolution of Operating Systems
•Batch processing
– One job (task) at a time
– Operating systems developed
• Programs to make computers more convenient to use
• Switch jobs easier
• Multiprogramming
– “Simultaneous” jobs
– Timesharing operating systems
Personal, Distributed & Client/Server Computing
•Personal computing
– Computers for personal use
• Distributed computing
– Computing performed among several computers
• Client/server computing
– Servers offer common store of programs and data
– Clients access programs and data from server
Machine Languages, Assembly Languages & High-Level Languages
•Machine language
– “Natural language” of computer component
– Machine dependent
• Assembly language
– English-like abbreviations represent computer operations
– Translator programs convert to machine language
• High-level language
– Allows for writing more “English-like” instructions
• Contains commonly used mathematical operations
– Compiler convert to machine language
• Interpreter
– Execute high-level language programs without compilation
History of C++
•C++
– Evolved from C
• Evolved from BCPL and B
– Provides object-oriented programming capabilities
• Objects
– Reusable software components that model real-world items
History of Java
•Java
– Originally for intelligent consumer-electronic devices
– Then used for creating Web pages with dynamic content
– Now also used for:
• Develop large-scale enterprise applications
• Enhance WWW server functionality
• Provide applications for consumer devices (cell phones, etc.)
Java Class Libraries
•Classes
– Include methods that perform tasks
• Return information after task completion
– Used to build Java programs
• Java contains class libraries
– Known as Java APIs (Application Programming Interfaces)
FORTRAN, COBOL, Pascal and Ada
•FORTRAN
– FORmula TRANslator
• COBOL
– COmmon Business Oriented Language
• Pascal
– Structured programming
• Ada
– Multitasking
BASIC, Visual Basic, Visual C++, C# and .NET
•BASIC
– Beginner’s All-Purpose Symbolic Instruction Code
• Visual Basic .NET
– Framework Class Library (FLC)
• Visual C++
– Microsoft Foundation Classes (MFC)
• C#
– C-Sharp
• .NET
– .NET platform
The Internet and the World Wide Web
•Internet
– Developed more than four decades ago
– Originally for connecting few main computer systems
– Now accessible by hundreds of millions of computers
• World Wide Web (WWW)
– Allows for locating/viewing multimedia-based documents
Basics of a Typical Java Environment
Java programs normally undergo five phases:
1– Edit
• Programmer writes program (and stores program on disk)
2– Compile
• Compiler creates byte codes from program
3– Load
• Class loader stores byte codes in memory
4– Verify
• Verifier ensures byte codes do not violate security requirements
5– Execute
• Interpreter translates byte codes into machine language
Fig. 1.1 A typical Java Environment
Thinking About Objects: Introduction to Object Technology and the Unified Modeling Language
•Object orientation
•
Unified Modeling Language (UML)
–
Graphical language that uses common notation
–
Allows developers to represent object-oriented designs
•Objects
–
Reusable software components that model real-world items
–
Look all around you
•
People, animals, plants, cars, etc.
–
Attributes
•
Size, shape, color, weight, etc.
–
Behaviors
•
Babies cry, crawl, sleep, etc.
•Object-oriented design (OOD)
–
Models real-world objects
–
Models communication among objects
–
Encapsulates attributes and operations (behaviors)
•
Information hiding
•
Communication through well-defined interfaces
•
Object-oriented language
–
Programming in object oriented languages is called object-oriented programming
(OOP)
–
Java
•Object-Oriented Analysis and Design (OOA/D)
–
Essential for large programs
–
Analyze program requirements, then develop solution
–
UML
•
Unified Modeling Language
•History of the UML
–
Need developed for process with which to approach OOA/D
–
Brainchild of Booch, Rumbaugh and Jacobson
–
Object Management Group (OMG) supervised
–
Version 2.0 is current version (released in 2003)
•UML
–
Graphical representation scheme
–
Enables developers to model object-oriented systems
–
Flexible and extendible
Discovering Design Patterns: Introduction
•Effective design crucial for large programs
• Design patterns
– Proven architectures for developing object-oriented software
• Architectures created from accumulated industry experience
– Reduce design-process complexity
– Promotes design reuse in future systems
– Helps identify common design mistakes and pitfalls
– Helps design independently of implementation language
– Establishes common design “vocabulary”
– Shortens design phase in software-development process
•Design patterns
– Similar to architectural elements
– Used by developers to construct sets of classes and objects
• Developers
– Familiarity with patterns to understand how to use patterns