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Basic Principles of CSS Design

Tue, 16 Mar 2010 02:17:48 +0000

Cascading Style Sheets (CSS) is a simple mechanism for adding style (e.g. fonts, colors, spacing) to Web document.

• Reduces code.
• Flexibility to change/modify changes across sites.

Why is it Called CSS

The Cascading Effect -

< head >
< link type="text / css" rel="stylesheet" href=“a / style.css" >
< link type="text / css" rel="stylesheet" href=“b / style.css" >
< link type="text / css" rel="stylesheet" href=“c / style.css" >
< /head >

Ways of CSS Implementation

a] Within a tag itself (inline styles)

< body style=“color: black; background: white;” >

b] Within a page and in it’s tag

c] Linking to a separate style sheet

< link type="text/css" rel="stylesheet" href="style.css" / >

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The Class Loader and Bytecode Verifier

Nanya — Sat, 13 Mar 2010 08:09:15 +0000

• Loads all classes necessary for the execution of a program
• Maintains classes of the local file system in separate namespaces
• Prevents spoofing
• The Bytecode Verifier ensures that:
   -The code adheres to the JVM specification.
   -The code does not violate system integrity.
   -The code causes no operand stack overflows or underflows.
   -The parameter types for all operational code are correct.
   -No illegal data conversions (the conversion of integers to pointers) have occurred.

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Garbage Collection and JVM implementations

Nanya — Sat, 13 Mar 2010 08:01:56 +0000

• Allocated memory that is no longer needed should be deallocated.
• In other languages, deallocation is the programmer’s responsibility.
• The Java programming language provides a system-level thread to track memory allocation.
• Garbage collection has the following characteristics:
   – Checks for and frees memory no longer needed
   – Is done automatically
   – Can vary dramatically across JVM implementations

JVM Tasks

• The JVM performs three main tasks:
   – Loads code
   – Verifies code
   – Executes code

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The Java Virtual Machine

Nanya — Sat, 13 Mar 2010 07:50:30 +0000

• Provides hardware platform specifications
• Reads compiled byte codes that are platform-independent
• Is implemented as software or hardware
• Is implemented in a Java technology development tool or a Web browser
• JVM provides definitions for the:
   – Instruction set (central processing unit [CPU])
   – Register set
   – Class file format
   – Stack
   – Garbage-collected heap
   – Memory area
• Fatal error reporting
• High-precision timing support
• The majority of type checking is done when the code is compiled.
• Implementation of the JVM approved by Sun Microsystems must be able to run any compliant class file.
• The JVM executes on multiple operating environments.

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Primary Goals of the Java Technology

Nanya — Sat, 13 Mar 2010 07:35:31 +0000

Provides an easy-to-use language by:

• Avoiding many pitfalls of other languages
• Being object-oriented
• Enabling users to create streamlined and clear code
• Provides an interpreted environment for
1.Improved speed of development
2.Code portability
• Enables users to run more than one thread of activity
• Loads classes dynamically; that is, at the time they are actually needed
• Supports changing programs dynamically during runtime by loading classes from disparate sources
• Furnishes better security
• The following features of java fulfill these goal
1.The Java Virtual Machine (JVM™)1
2.Garbage collection
3.The Java Runtime Environment (JRE)
4.JVM tool interface

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Java Technology and its Key Concepts

Nanya — Sat, 13 Mar 2010 07:17:31 +0000

What Is the Java Technology?

Java technology is:

– A programming language
– A development environment
– An application environment
– A deployment environment

• Java Technology is similar in syntax to C++.

• It is used for developing both applets and applications.

Key features of Java

• Object-oriented
• Distributed
• Simple
• Multithreaded
• Secure
• Platform-independent

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History of JAVA

Nanya — Sat, 13 Mar 2010 07:09:14 +0000

Here are the key aspects of History of Java -

• Jan 96 -Java Development Kit 1.0 (JDK 1.0).

• Dec 98 -Java 2 Platform with version 1.2 of the Software Development Kit (SDK 1.2).

• Aug 99 -Java 2 Platform, Standard Edition (J2SE).

• Dec 99 -Java 2 Platform, Enterprise Edition (J2EE).

• May 2000 -J2SE with version 1.3 of the SDK.

• Today - J2SE with version 1.5 of the SDK.

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Introduction to DHTML

YourOnlineTutor — Tue, 09 Mar 2010 21:57:22 +0000

DHTML is an entirely “client-side” technology

- It does not require plugins and embeds seamlessly into a web page.

- Underlying technologies-HTML, CSS, javaScript

- Allows changing of content, color, fonts, etc. dynamically

What is DHTML?

It is considered to be made up of HTML, Cascading Style Sheets (CSS), and Scripting language.

All three of these components are linked via Document Object Model (DOM).

DOM

For those who don’t know about DOM, it is the interface that allows scripting languages to access the content, style, and structure of the web documents and change them dynamically

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What is RDF?

Wed, 03 Feb 2010 06:17:59 +0000

The resource description framework (RDF), is an XML-based application being developed in the W3C…

It brings together ideas from the meta content format, or MCF (technology acquired by Netscape from Apple Computer Inc.) and XML-Data (defined in a proposal recently submitted to the W3C by Microsoft, ArborText, DataChannel, and Inso).

RDF allows for generalized searching of information without application-specific rules, such as those defined in DTDs. RDF allows a complementary view of data through graphs and nodes, rather than through a structured tree, which the current XML technology enables. RDF, together with XML schemas, will provide a standard way for developers to write these relationships down for broad classes of XML elements.

The crucial technologies that will deliver value this year and next are XML for structured data, XML namespaces to make names unique and recognizable, and new XML tags that add meaning to data so smarter search engines can perform better searches.

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Insight to Cookies: Advanced Programming Concepts

Fri, 06 Nov 2009 20:07:31 +0000

Here’s more info on cookies that you may want to know -

• When the cookie is requested for the first time, the cookie is stored using the set-Cookie entry in the header of the response from the server.
• Set-cookie : name= value; expires = Date;Path=PATH;domain=DOMAIN;secure

Optional attributes are –

• Expires =Date
• Path=PATH ( path of the URL for which the cookie is valid)
• Domain – Domain specifies the domain for which the cookie is valid.
• Secure specifies that the cookie has to be transmitted only over a secure link.
• Exampleofcookies

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