Hardware / Software Trends and Programming (in Chapter 1) OBJECTIVES. Chapter 1 Sections

Transcription

1 Internet & World Wide Web: How to Program by Deitel and Deitel Hardware / Software Trends and Programming (in Chapter 1) 1/19/ OBJECTIVES In this chapter you will learn about: basic computing concepts. the different types of programming languages. the evolution of the Internet and the World Wide Web. what Web 2.0 is and why it s having such an impact among Internet-based and traditional businesses. what Rich Internet Applications (RIAs) are and the key software technologies used to build RIAs. 2 Chapter 1 Sections 1.8 Personal, Distributed and Client/Server Computing 1.9 Hardware Trends 1.10 Key Software Trend: Object Technology 1.11 JavaScript: Object-Based Scripting for the Web 1.12 Browser Portability C, C++ and Java 1.14 BASIC, Visual Basic, Visual C++, C# and.net 1.15 Software Technologies 1.16 Notes about Internet & World Wide Web How to Program, 4/e 1.17 Web Resources 3 1

2 Personal, Distributed and Client/Server Computing Personal Computing 1977 Apple Computer popularized personal computing computers became economical for personal or desktop business use 1981 IBM PC Distributed Computing workstations could be linked together in computer networks (late 1980s) Local area networks (LANs) Client/Server Computing servers offer data storage and other capabilities that may be used by client computers distributed throughout the network, popular operating systems for C/S UNIX, Linux, Mac OS X and Microsoft s Windows 4 Hardware Trends Cost of products and services consistently dropping over the decades Computer capacity and speed doubles every two years (on average)» Moore s Law Microprocessor chip laid groundwork in late 1970s and 1980s for productivity improvements of the 1990s hardware moving toward mobile, wireless technology hand-held devices more powerful than early supercomputers portability wireless data-transfer speeds 5 Key Software Trend: Object Technology Objects reusable software components that model items in the real world (classes) makes software developers more productive do not have to reinvent the wheel object-oriented programs often easier to understand, correct and modify than older types of programs 6 2

3 Key Software Trend: Object Technology (cont.) Packaging scheme that helps create meaningful software units large and highly focused on particular applications areas Before object technology, programming languages focused on actions (verbs) rather than on objects (nouns) programmers programmed (wrote code) primarily with verbs made programs awkward, hard to read the real world is filled with complex objects and simple actions 7 Key Software Trend: Object Technology (cont.) Object-oriented programming programmers work in ways that complement how they see the world more natural process significant productivity enhancements Procedural programming code was not particularly reusable forced programmers to constantly reinvent the wheel waste of time and resources Objects (classes) software modules kept in libraries (electronic) reusable save time and resources 8 Objects Have attributes properties characteristics color, size, shape, weight Exhibit behaviors operations a ball rolls a balloon deflates a baby cries 9 3

4 Object Classification Observe object behaviors Study object attributes Group objects with similar attributes, behaviors Compare objects chimpanzees adult human baby lizard 10 Object-Oriented Software Design OOD Model software in terms similar to those used to describe real-world objects Classes of objects have similar characteristics cars, trucks, little red wagons, roller skates all have wheels class convertible is a subclass of the class automobile 11 Objects Interact People objects send information to other people objects by talking A bank account object send a message to another object that an account has a negative balance 12 4

5 OOD Encapsulates: ties together an object s attributes and behaviors Hides Information: The way properties or operations are implemented are hidden from a user of the object (a developer is a user of the object when she uses it in a section of code) Interface: The means by which the object communicates with users of the object 13 Object-oriented vs. Procedural VB.NET is object-oriented C is procedural Object-oriented programming: Programming in an object-oriented language fundamental unit is the class a class has properties and methods Procedural programming: action oriented programming where actions are defined by procedures Fundamental unit is the function or procedure 14 Classes, Fields, Methods Class is a user-defined type contains data attributes, properties, fields contains methods that manipulate data Classes can be associated with other classes relationships 15 5

6 Component Software Group of related classes Reusable employ it in multiple applications 16 Object-oriented Analysis and Design Process Requirements what is the system supposed to do? Specification how will the system do what it s supposed to do? Pseudocode: informal textual description of program flow and logic OK for small programs/systems Systems analysis and design software 17 Unified Modeling Language UML Most widely used graphical representation for modeling object-oriented systems Extensible: can be enhanced with new features Independent of OOAD process used A feature-rich graphical language 18 6

7 Software Engineering Observations Extensive class libraries of reusable software components are available on the Internet. Many of these libraries are free. Some organizations report that the key benefit object- oriented programming gives them is not software that is reusable but, rather, software that is more understandable, better organized and easier to maintain, modify and debug. This can be significant, because perhaps as much as 80 percent of software cost is associated not with the original efforts to develop the software, but with the continued evolution and maintenance of that software throughout its lifetime. 19 Software Engineering Observation Reuse of existing classes when building new classes and programs saves time, money and effort. Reuse also helps programmers build more reliable and effective systems, because existing classes and components often have gone through extensive testing, debugging and performance tuning. 20 JavaScript Offers object-based scripting for the Web Attractive language for advancing one s level of programming skill object-based language supports proper software engineering techniques free for download interpreter built into today s most popular p Web browsers powerful scripting language portable programs execute interpretively on client machines when run through a browser ActionScript and JavaScript are converging in the next version of the JavaScript standard (JavaScript 2/ECMA Script version 4) universal client scripting language simplifies web application development 21 7

8 What is Ecma? Ecma International is an industry association founded in 1961 and dedicated to the standardization of Information and Communication Technology (ICT) and Consumer Electronics (CE) Prior to 1994 it was known as ECMA - European Computer Manufacturers Association Microsoft instrumental in the standardization of JavaScript by ECMA 22 Ready or not Programming 23 Good Programming Practice Write your programs in a simple and straightforward manner. This is sometimes referred to as KIS ( keep it simple ). One key aspect of keeping it simple is another interpretation of KIS keep it small. 24 8

9 Portability Tips 25 It is easier to write portable programs in JavaScript than in many other programming languages. However, differences among interpreters and browsers make portability difficult to achieve. Simply writing programs in JavaScript does not guarantee portability. Research platform variations and write code accordingly. Portability Tips 26 When writing JavaScript programs, you need to deal directly with crossbrowser portability issues. Such issues are hidden by JavaScript libraries i (e.g., Dojo, Prototype, Script.aculo.us and ASP.NET Ajax). These libraries provide powerful, ready-to-use capabilities that simplify JavaScript coding, making it cross-browser compatible. Error-Prevention Tips Always test your JavaScript programs on all systems and in all web browsers for which they are intended. 27 9

10 Good Programming Practice Read the documentation for the JavaScript version you are using to access JavaScript s rich collection of features. 28 Error-Prevention Tips Your computer and JavaScript interpreter are good teachers. If you are not sure how a feature works, even after studying the documentation, experiment and see what happens. Study each error or warning message and adjust the code accordingly. 29 Portability of Programs Across Browsers A great challenge much diversity of client browsers in use many different platforms in use Difficult to know capabilities and features of all browsers and platforms in use find correct mix between absolute portability, complexity and usability of features 30 10

11 Portability Tips The web is populated with many different browsers, which makes it difficult for authors and web application developers to create universal solutions. The W3C is working toward the goal of a universal client-side platform. 31 Here we go Programming Languages 32 C, C++ and Java C developed by Dennis Ritchie at Bell Laboratories development language of the UNIX operating system virtually all new major operating systems are written in C and/or C++ C++ developed by Bjarne Stroustrup in early 1980s spruce up the C language provide capabilities for object-oriented programming (OOP) Java developed by Sun Microsystems in 1991 Sun saw the immediate potential of using Java to add dynamic content (e.g., interactivity, animations and the like) to web pages Sun formally announced Java at an industry conference in May 1995 Java is now used to develop large-scale enterprise applications enhance the functionality of web servers provide applications for consumer devices 33 11

12 BASIC, Visual Basic, Visual C++, C# and.net BASIC developed in the mid-1960s at Dartmouth College stands for Beginner s All-Purpose Symbolic Instruction Code primary purpose was to familiarize novices with programming techniques Microsoft s Visual Basic language based on BASIC added a development environment that facilitated GUI development has become one of the most popular programming languages in the world Microsoft s.net development platform provides the capabilities developers need to create computer applications that can execute on computers distributed across the Internet Visual Basic (based on the original BASIC) Visual C++ (based on C++) 34 Visual C# (based on C++ and Java) Software Technologies Agile Software Development set of methodologies that try to get software developed and implemented quickly agile Alliance ( agile Manifesto ( Refactoring reworking code to make it clearer and easier to maintain from a programmer perspective does not alter the external behavior of the code, rather improves its internal structure Design patterns proven architectures for constructing flexible and maintainable object-oriented software open source code 35 Software Technologies (cont.) Linux open source operating system Apache most popular open source web server MySQL open source database management system PHP most popular open source server-side scripting language for developing Internet-based applications LAMP Linux, Apache, MySQL and PHP (or Perl or Python) Game programming software techniques used in game programming Adobe, Flash, CS3 Ruby on Rails Combines the scripting language Ruby with the Rails web application framework Developed by 37Signals Software as a Service (SaaS) software runs on servers elsewhere on the Internet Salesforce.com, Google, Microsoft and 37Signals all offer SaaS 36 12

13 Microsoft s.net Embraces the Internet and WWW in the arena of software development Language independent Web services: extends the idea of reusable software components to Internet application development 37 The.NET Framework and the CLR Framework: manages and executes applications manages and executes Web services contains a class library enforces security Details of the Framework are in the Common Language Infrastructure (CLI) CLI is ECMA Standard 335 compliant 38.NET Languages.NET programming languages APL Mondrian Visual C# Oberon COBOL Oz Component Pascal Pascal.NET framework can work with programs written in many languages Curriculum Eiffel Forth Fortran Haskell Java JScript Mercury Perl Python RPG Scheme Smalltalk Standard ML Visual Basic Visual C++ 13

14 CLR CLR: Common Language Runtime Executes.NET programs.net programs are compiled first into Microsoft Intermediate Language (MSIL) MSIL defines the language understood d by the CLR MSIL for an application is in the.exe file When you run the.exe the CLR just-in-time compiler translates the MSIL into the machine language for a particular platform 40 Platform Independence Install the.net Framework on the platform for which it s created and any.net application can be run without modification regardless if the development language is Visual Basic, C++, Fortran, 41 Internet & World Wide Web: How to Program by Deitel and Deitel End of Slides for Chapter 01 Part 03 1/19/