Data must be accurately stored and delivered and unnecessary data must be deleted. Data cleansing must be taken with utmost care because the lifeline of the company relies on them. Often in a vast database, errors inevitably occur in the system this is a very high threat to the company's database. The objective of data cleansing is to eliminate or minimize data errors to...
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Tuesday, August 25, 2009
what is HTML?
HTML stands for Hyper Text Markup Language. It is a type of computer language that is primarily used for files that are posted on the internet and viewed by web browsers. HTML files can also be sent via email.
Although it may seem complex to the uninitiated, HTML is relatively simple. All text, graphics and design elements of a web page are "tagged" with codes that instruct the web browser how to display the files. Such files are easy to recognize because they contain the file extension of 'html' or 'htm'.
In addition to the page content itself, HTML files provide layout and formatting information. HTML is not case sensitive and can be easily updated after the file is created. For the novice web designer, there are many different software utilities and programs available to assist in generating HTML pages.
To format a simple text file into HTML, the user creates tags that start and finish with angle brackets. To end the formatting or change to another format, the HTML developer types the first angle bracket, a backslash, then repeats the command and closes the bracket. For example,
Although it may seem complex to the uninitiated, HTML is relatively simple. All text, graphics and design elements of a web page are "tagged" with codes that instruct the web browser how to display the files. Such files are easy to recognize because they contain the file extension of 'html' or 'htm'.
In addition to the page content itself, HTML files provide layout and formatting information. HTML is not case sensitive and can be easily updated after the file is created. For the novice web designer, there are many different software utilities and programs available to assist in generating HTML pages.
To format a simple text file into HTML, the user creates tags that start and finish with angle brackets. To end the formatting or change to another format, the HTML developer types the first angle bracket, a backslash, then repeats the command and closes the bracket. For example,
What is HTML?
is the code used to create the heading at the top of this article.There are different codes for all sorts of other formatting including italics, tables, paragraphs etc. The "A" tag is used to designate words that are to be displayed as hyperlinks to other pages.
If you would like to view a sample of HTML, a good place to start might be the code that was used to generate this very page. Simply click on the "view" menu on your browser and then select "source". It may look complicated, but if you learned the limited number of tags, you would discover that it is a relatively straightforward language.
What is a CSS?
- A Cascading Style Sheet (CSS) is a list of statements (also known as rules) that can assign various rendering properties to HTML elements. Style rules can be specified for a single element occurrence, multiple elements, an entire document, or even multiple documents at once. It is possible to specify many different rules for an element in different locations using different methods. All these rules are collected and merged (known as a "cascading" of styles) when the document is rendered to form a single style rule for each element.
What is SQL?
Structured Query Language (SQL) is a specialized language for updating, deleting, and requesting information from databases. SQL is an ANSI and ISO standard, and is the de facto standard database query language. A variety of established database products support SQL, including products from Oracle and Microsoft SQL Server. It is widely used in both industry and academia, often for enormous, complex databases.
In a distributed database system, a program often referred to as the database's "back end" runs constantly on a server, interpreting data files on the server as a standard relational database. Programs on client computers allow users to manipulate that data, using tables, columns, rows, and fields. To do this, client programs send SQL statements to the server. The server then processes these statements and returns replies to the client program.
SELECT list_of_column_names from list_of_relation_names where conditional_expression_that_identifies_specific_rows
SELECT * FROM Customers WHERE Last_Name='Smith'; The server back end may then reply with data such as this:
+---------+-----------+------------+ | Cust_No | Last_Name | First_Name | +---------+-----------+------------+ | 1001 | Smith | John | | 2039 | Smith | David | | 2098 | Smith | Matthew | +---------+-----------+------------+ 3 rows in set (0.05 sec)
In a distributed database system, a program often referred to as the database's "back end" runs constantly on a server, interpreting data files on the server as a standard relational database. Programs on client computers allow users to manipulate that data, using tables, columns, rows, and fields. To do this, client programs send SQL statements to the server. The server then processes these statements and returns replies to the client program.
Examples
To illustrate, consider a simple SQL command, SELECT. SELECT retrieves a set of data from the database according to some criteria, using the syntax:SELECT list_of_column_names from list_of_relation_names where conditional_expression_that_identifies_specific_rows
- The
list_of_relation_namesmay be one or more comma-separated table names or an expression operating on whole tables
- The
conditional_expressionwill contain assertions about the values of individual columns within individual rows within a table, and only those rows meeting the assertions will be selected. Conditional expressions within SQL are very similar to conditional expressions found in most programming languages.
Customers all records (designated by the asterisk) with a value of Smith for the column Last_Name, a client program would prepare and send this SQL statement to the server back end: SELECT * FROM Customers WHERE Last_Name='Smith'; The server back end may then reply with data such as this:
+---------+-----------+------------+ | Cust_No | Last_Name | First_Name | +---------+-----------+------------+ | 1001 | Smith | John | | 2039 | Smith | David | | 2098 | Smith | Matthew | +---------+-----------+------------+ 3 rows in set (0.05 sec)
What is C++?
C++ is an "object oriented" programming language created by Bjarne Stroustrup and released in 1985. It implements "data abstraction" using a concept called "classes", along with other features to allow object-oriented programming. Parts of the C++ program are easily reusable and extensible; existing code is easily modifiable without actually having to change the code. C++ adds a concept called "operator overloading" not seen in the earlier OOP languages and it makes the creation of libraries much cleaner.
C++ maintains aspects of the C programming language, yet has features which simplify memory management. Additionally, some of the features of C++ allow low-level access to memory but also contain high level features.
C++ could be considered a superset of C. C programs will run in C++ compilers. C uses structured programming concepts and techniques while C++ uses object oriented programming and classes which focus on data.
C++ maintains aspects of the C programming language, yet has features which simplify memory management. Additionally, some of the features of C++ allow low-level access to memory but also contain high level features.
C++ could be considered a superset of C. C programs will run in C++ compilers. C uses structured programming concepts and techniques while C++ uses object oriented programming and classes which focus on data.
PHP? what it does?
Anything. PHP is mainly focused on server-side scripting, so you can do anything any other CGI program can do, such as collect form data, generate dynamic page content, or send and receive cookies. But PHP can do much more.
There are three main areas where PHP scripts are used.
Server-side scripting. This is the most traditional and main target field for PHP. You need three things to make this work. The PHP parser (CGI or server module), a web server and a web browser. You need to run the web server, with a connected PHP installation. You can access the PHP program output with a web browser, viewing the PHP page through the server. All these can run on your home machine if you are just experimenting with PHP programming.Command line scripting. You can make a PHP script to run it without any server or browser. You only need the PHP parser to use it this way. This type of usage is ideal for scripts regularly executed using cron (on *nix or Linux) or Task Scheduler (on Windows). These scripts can also be used for simple text processing tasks.
Writing desktop applications. PHP is probably not the very best language to create a desktop application with a graphical user interface, but if you know PHP very well, and would like to use some advanced PHP features in your client-side applications you can also use PHP-GTK to write such programs. You also have the ability to write cross-platform applications this way. PHP-GTK is an extension to PHP, not available in the main distribution.
PHP can be used on all major operating systems, including Linux, many Unix variants (including HP-UX, Solaris and OpenBSD), Microsoft Windows, Mac OS X, RISC OS, and probably others. PHP has also support for most of the web servers today. This includes Apache, Microsoft Internet Information Server, Personal Web Server, Netscape and iPlanet servers, Oreilly Website Pro server, Caudium, Xitami, OmniHTTPd, and many others. For the majority of the servers, PHP has a module, for the others supporting the CGI standard, PHP can work as a CGI processor.
So with PHP, you have the freedom of choosing an operating system and a web server. Furthermore, you also have the choice of using procedural programming or object oriented programming, or a mixture of them. Although not every standard OOP feature is implemented in PHP 4, many code libraries and large applications (including the PEAR library) are written only using OOP code. PHP 5 fixes the OOP related weaknesses of PHP 4, and introduces a complete object model.
With PHP you are not limited to output HTML. PHP's abilities includes outputting images, PDF files and even Flash movies (using libswf and Ming) generated on the fly. You can also output easily any text, such as XHTML and any other XML file. PHP can autogenerate these files, and save them in the file system, instead of printing it out, forming a server-side cache for your dynamic content.
What is Object Oriented Programming?
Everyone that wants to program JavaScript should at least try reading the following section. If you have trouble understanding it, don't worry. The best way to learn JavaScript is from the examples presented in this tutorial. After you have been through the lessons, come back to this page and read it again.
OOP is a programming technique (note: not a language structure - you don't even need an object-oriented language to program in an object-oriented fashion) designed to simplify complicated programming concepts. In essence, object-oriented programming revolves around the idea of user- and system-defined chunks of data, and controlled means of accessing and modifying those chunks.
Object-oriented programming consists of Objects, Methods and Properties. An object is basically a black box which stores some information. It may have a way for you to read that information and a way for you to write to, or change, that information. It may also have other less obvious ways of interacting with the information.
Some of the information in the object may actually be directly accessible; other information may require you to use a method to access it - perhaps because the way the information is stored internally is of no use to you, or because only certain things can be written into that information space and the object needs to check that you're not going outside those limits.
The directly accessible bits of information in the object are its properties. The difference between data accessed via properties and data accessed via methods is that with properties, you see exactly what you're doing to the object; with methods, unless you created the object yourself, you just see the effects of what you're doing.
Other Javascript pages you read will probably refer frequently to objects, events, methods, and properties. This tutorial will teach by example, without focusing too heavily on OOP vocabulary. However, you will need a basic understanding of these terms to use other JavaScript references.
OOP is a programming technique (note: not a language structure - you don't even need an object-oriented language to program in an object-oriented fashion) designed to simplify complicated programming concepts. In essence, object-oriented programming revolves around the idea of user- and system-defined chunks of data, and controlled means of accessing and modifying those chunks.
Object-oriented programming consists of Objects, Methods and Properties. An object is basically a black box which stores some information. It may have a way for you to read that information and a way for you to write to, or change, that information. It may also have other less obvious ways of interacting with the information.
Some of the information in the object may actually be directly accessible; other information may require you to use a method to access it - perhaps because the way the information is stored internally is of no use to you, or because only certain things can be written into that information space and the object needs to check that you're not going outside those limits.
The directly accessible bits of information in the object are its properties. The difference between data accessed via properties and data accessed via methods is that with properties, you see exactly what you're doing to the object; with methods, unless you created the object yourself, you just see the effects of what you're doing.
Other Javascript pages you read will probably refer frequently to objects, events, methods, and properties. This tutorial will teach by example, without focusing too heavily on OOP vocabulary. However, you will need a basic understanding of these terms to use other JavaScript references.
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