Important connectivity in network system

Connectivity សំខាន់ៗក្នុងប្រព័ន្ធ Network

Connectivity ជាឧបករណ៍សំរាប់ប្រើក្នុងភ្ជាប់និងតំលើងប្រព័ន្ធ Network មានច្រើនប្រភេទ ហើយធ្វើការផ្សេងៗគ្នាទៅតាមតំរូវការរបស់ប្រព័ន្ធ Network របស់លោកអ្នក ។ Connectivity ដែលគេនិយមប្រើច្រើនក្នុងប្រព័ន្ធ Network ពេលបច្ចុប្បននេះមានដូចជា: Modem, Hub, Switch និង Router ។

1. Modem

Medem ជាប្រភេទ Connectivity មួយប្រភេទដែលធ្វើការ translate ពី digital signal ទៅជា analog signal និងពី analog signal មកជា digital signal វិញ ។ ជាទូទៅគេប្រើ Modem ក្នុងប្រព័ន្ធ Network សំរាប់ភ្ជាប់តាមរយៈ Dial-up និងការភ្ជាប់ Internet តាមរយៈ DLS ។

2. Hub

Hub ជាឧបករណ៍មួយដែលដើតួរជា Station សំរាប់ធ្វើការបែងចែកនូវ Connection ទៅអោយ Computer ផ្សេងៗដើម្បីបង្កើតបានជាប្រព័ន្ធ Network ។ ការងារបស់ Hub គឺនៅពេលមានទិន្ន័យឆ្លងកាត់ Hub បានធ្វើរការ Broadcast ទៅកាន់គ្រប់គ្រប់ Connection ទាំងអស់ដែលធ្វើភ្ជាប់ជាមួយ Hub ។ Hub ចែកជា ៣ ប្រភេទគឺ Passive Hub, Active Hub និង Intelligent Hub ។

• Passive Hub: ជា Hub មួយប្រភេទនៅពេលមានទិន្ន័យឆ្លងកាត់មិនធ្វើការ តំលើងនូវ Signal ទេហើយធ្វើការ Broadcast ទៅគ្រប់ Connection តែម្តង ។
• Active Hub: ជា Hub មួយប្រភេទដែលធ្វើការខុសពី Passive Hub ដោយនៅពេលមាន Signal ឆ្លងកាត់ Active Hub ធ្វើរការតំលើងនូវ Signal រួចទើបធ្វើរការ Broadcast ទៅកាន់គ្រប់ Connection ។ គុណសម្បត្តិរបស់ Active Hub គឺជួយកាត់បន្ថយនូវ error បញ្ចូន data និងធ្វើអោយចំងាយនៃការបញ្ចូន data បានចំងាយឆ្ងាយ ។
• Intelligent Hub: គឺជា Active Hub ដែលបន្ថែមនូវ feature ថ្មីៗដែលជួយគ្រប់គ្រងនូវប្រព័ន្ធ network និងធ្វើអោយ performance network មានភាពប្រសើរឡើង ។ Feature ថ្មីរបស់ Intelligent Hub មានពីគឺ: Hub Management និង Switching Hub ។
• Hub Management: ដែលអាចបញ្ចូន Packet ទៅកាន់ central network console ដោយប្រើ network management protocol ។ Hub ប្រភេទនេះអាចបញ្ឈប់នូវ connection ដែលធ្វើអោយ network error ។
• Switching Hub: ជាបច្ចេកវិទ្យាចុងក្រោយរបស់ hub ដែលមានល្បឿនលឿនក្នុងការបញ្ចូន data ព្រោះ Switching hub ធ្វើការ route signal ទៅកាន់ Destination Computer ដោយមិនធ្វើការ broadcast ទៅគ្រប់ port ដូច Passive និង Active hub ទេ ។

3. Switch:

Switch ជាឧបករណ៍មួយដែលដើរតួរជា station សំរាប់ភ្ចាប់ connection network ដូចជា Hub ដែលប៉ុន្តែ Switch មិនធ្វើការដូចជា Hub ទេ ។ Switch ធ្វើការបញ្ចូន Data មានល្បឿនលឿនជាង Hub ដោយមិនធ្វើការ Broadcast ទៅកាន់គ្រប់ port ដូច Hub ទេគឺ Switch បានធ្វើការបញ្ចូន Data ទាំងនោះទៅកាន់ Destination Computer ដោយផ្ទាល់តែម្តង ។

4. Router

Router ជាឧបករណ៍ connectivity មួយប្រភេទដែលមានតួរនាទីច្រើន និងសំខាន់ក្នុងប្រព័ន្ធ Network ។ Router អាចយកមកធ្វើជា Gateway សំរាប់ធ្វើអោយប្រព័ន្ធ Network ផ្សេងគ្នាអាចដំនើរការជាមួយគ្នាបាន ។ Router ក៏ជាឧបករណ៍មួយដែលអាចធ្វើជា Firewall បានទៀតផងព្រោះនៅក្នុង Router មាន Option សំរាប់កំនត់នូវ port, protocol រឺ domain ដែលអនុញ្ញាតិ រឺមិនអនុញ្ញាតិអោយឆ្លង់កាត់ Router ។ ជាងនេះទៅទៀត Router ជាឧបករណ៍មួយដែលមានសម្ថភាពខ្ពស់ក្នុងការ route data ទៅកាន់ Destination ព្រោះនៅក្នុង Router មាន routing table សំរាប់កត់ចំនាំនូវ Network address របស់កុំព្យូទ័រផ្សេងៗនៅក្នុងប្រព័ន្ធ network ដើម្បីធ្វើអោយមានល្បឿនលឿន នៅពេល route data ។

Why is my computer so slow

1. It's possible that your computer may have so many background programs running that there is not enough main memory to run your main programs. All icons in your computer's system tray are background programs using memory.
To see and remove all running background programs:
a. Press the Ctrl + Alt + Delete keys at the same time.
b. Click any program or task except Explorer or Systray.
c. Then click End Task.
Repeat steps b and c to quit all programs except Explorer and Systray which are necessary components of Microsoft Windows.

You should now have a clean system, however you have just removed the programs from your computer's memory, they will all return the next time you start Windows.
If you don't want certain background programs starting when you boot, use the Start/Search function to find the program and either configure it not to run at startup, remove it from Programs/Startup, or delete it from your system.
 

2. Your hard drive could be too full of data to function efficiently. There should be at least 300MB-500MBs of free space to allow for disk file chores. Note that this mostly applies to the C: drive or whatever drive your Window's cache is on.
If your C: drive is too full, delete unused programs on the C: drive to make space.
PC Cleaner and other similar programs, can and should be used to clean uneeded files, internet caches, and other junk from your hard drive.

3. Your computer could have a fragmented hard drive. This results from programs being loaded and deleted. To avoid this problem, run the Window's hard drive defragmenter (Defrag) once a month.

4. If you have 256 MB of free system memory or less, or you like to play games, you may not have enough system memory to run your software efficiently. You should probably upgrade to 512 MB or more of system memory. Newer systems running Windows 7 should have 1-2 GB of system memory as a minimum.

5. You could have old or conflicting Windows device drivers. An example would be you might actually have two entirely different video drivers on your system and Windows could actually be alternately using both of them.
To prevent this problem, First boot the computer in Safe Mode by pressing and holding the F8 key during startup, after the DOS memory check has completed.
While in Safe Mode select Start/Settings/Control Panel/System/Devices. Click on all the devices and see if the various drivers have any yellow or red exclamation marks (which indicates a driver conflict) and also determine if there are any duplicate drivers that can be eliminated.
You may have to delete and reload a driver to correct these problems. 

6. As each new Windows program is installed and uninstalled, it leaves behind parts of itself that can slow down or crash your computer. These are mostly .dlls and other shared files.
It's also very possible when uninstalling a program that needed Windows system files can be deleted. When your computer asks if you want to uninstall shared files it's usually safest to say no -- even if your uninstall program claims the files are not being used.
Old Windows drivers can be found by booting into Safe Mode, then opening Control Panel/System/Devices and ridding your system of old drivers.
Otherwise, the only real answer to getting all the old junk off your computer is to reload Windows into a new directory which eliminates all old junk and leftover files. This is something to do last, as you will also have to reload all your Windows settings, drivers, and programs. 

7. Your computer could be full of adware, spyware, viruses, or trojans. These are all nasty programs that will not only slow down your computer, they will literally take over the functioning of your computer. You definitely don't want any of these parasite programs on your computer. To get rid of these parasite programs, and to prevent them from installing in the first place, you need up-to-date firewall, anti-virus, and spyware removal programs.
These are three separate software programs that must be running at all times except for when you are not plugged into the Internet. It is very important that these programs continuously update themselves or they will become out-dated and will no longer be useful.

Dictionary Oxford Advance for PC with file crack

Free download

Dictionary Oxford Advance for PC with file crack

https://docs.google.com/file/d/0B7E8ImPoOrbcWEZVZ19RNWFFcG8/edit

Dictionary Oxford for Adroid

https://docs.google.com/file/d/0B7E8ImPoOrbcc29iMDJGYXBxdTg/edit

PHP

PHP Introuduce

PHP Processing and Testing Environments
1. Test on your live web server (easiest way for beginners) Most people starting in PHP development already have a web server online. Simply create your .php files, FTP them into your web directory and the server will parse them for you automatically. Most web hosts offer PHP support, and if your host does not, consider switching to a better one. If you do not have a web server online yet, buy a Domain Name for about $10 and set up a free or paid hosting account for that domain name. Be sure to choose PHP and not ASP if given a choice. Then you can FTP files to the server and test online. 2. Create a local testing environment on your computer Using a bundled environment software makes life easier: WAMP - http://www.wampserver.com/en/ XAMPP - http://www.apachefriends.org/en/xampp.html LAMP - https://www.linux.com/learn/tutorials/288158-easy-lamp-server-installation Or you can manually install the three components of your local PHP server onto your computer. PHP Core - http://www.php.net/downloads.php Apache Server - http://www.apache.org MySQL Database - http://dev.mysql.com/doc/

JavaScript

JavaScript Library

Javascript Introduction Share / Like

If you are new to Javascript let me be the first to welcome you to the world of web document programming. Javascript quite literally brings your html and css to life. One can view Javascript as the central nervous system of their web document, HTML as the skeleton, and CSS as the skin and fashion sense of the document.

In this particular guide we will tackle Javascript from the perspective of a webmaster and web application creator, while touching on topics important to game creators, animators, and multimedia programmers. I will assume you are proficient with HTML and CSS as I write this guide.
How It Works

It utilizes the Document Object model to target elements and properties of your web document. It also relies on HTML's event handling features to execute script in your documents in real time without requiring page refresh to alter the page elements. Javascript can run while your page loads, when people interact with something, according to timers you can program, and even when somebody tries to close or navigate away from your page. Javascript can control nearly everything on and about a web page. It handles user interaction, animation, form validation, dynamics, mathematics, and much more. Javascript is also part of what is known as Asynchronous JavaScript and XML(Ajax), which is a method used to make server and database calls behind the scenes and return data without the web document requiring refresh.
Similarity to Other Technologies

Javascript is similar to other scripting languages like C, Java, PHP, Actionscript 3.0 and many other programming technologies. The way that it works with variables, strings, functions, arrays, numbers, and objects is very similar to many technologies that came before it, and for sure many that will come after it. Since Javascript is somewhat similar to PHP and Actionscript 3.0, learning Javascript gives you an instant jump on learning any other type of popular scripting languages geared for the web or otherwise. If you happen to be coming from a programming background already, you will find Javascript to be a familiar walk in the park.
Transmission With Other Technologies

Javascript acts as a conduit of sorts that allows you to tap other technologies right into it. Javascript can tap into HTML and CSS no problem, PHP and Actionscript no sweat, MySQL and XML data transmissions are easy as pie with the myriad of technologies that communicate with Javascript. For instance Javascript cannot talk directly with a MySQL database to get data out of it, so we use Javascript(XMLHttpRequest object) to call on a PHP script that can talk direct to MySQL and transmit the database data straight back to Javascript for us to display in the document or do whatever evaluations upon.

CSS

CSS Introduction

CSS is yet another awesome technology maintained by the World Wide Web Consortium. CSS is an acronym that stands for Cascading Style Sheets. CSS is used by web masters to style their HTML elements for display on their web pages. CSS can also handle some application logic regarding user interaction that Javascript also handles.

CSS has two main components which make the magic happen:

CSS Selectors
CSS Properties

CSS works by allowing you to target your web page elements by using the CSS Selectors, then applying the various CSS Properties to your targeted elements.

As a webmaster and web applications creator I use external CSS to style my web pages and help me to keep my website more easily managed. Separating content from its styling logic becomes more important the larger your website becomes. And if you get into building large scale dynamic websites for clients, CSS is a must.

Within this CSS guide you can learn about the inner workings of CSS, as well as get real world CSS examples and tutorials to help you on your way. Don't forget that we have some video tutorials for CSS + HTML after you get cozy with CSS syntax and scan all of the properties/selectors at your disposal. The video tutorials may help you see application logic being formed.


CSS Levels and Summary of CSS History

CSS is a perpetual work in progress by the individuals who draft, develop and deploy it. Each time major enhancements are made to CSS it goes up in levels that build upon the previous levels. We are currently looking forward to CSS3 as the next recommended specification. CSS4 is on the drafting table as well. This site will attempt to keep it's library up to date regarding CSS as the technology evolves.

CSS level 1 - CSS1 is the first official release of the style recommendations set forth in 1996.

CSS level 2 - CSS2 is the 1998 release of recommended specifications to CSS.

CSS level 2 revision 1 - CSS2.1 is a revision that replaces the mechanics of CSS2 that lead to problems. Recommended as specification June 2011 by W3C.

CSS level 3 - Drafts to CSS3 started appearing in 1999. CSS3 is made more modular and extensible for browser software vendors than previous levels of CSS. CSS3 is made up of modules that browser software(user agent) creators can implement as they deem the modules worthy of implementation. CSS3 is not a complete recommended specification yet but more and more modules of CSS3 are getting implemented into various big name browsers.
CSS level 4 - Drafts of CSS4 began September 2009. None of its modules are supported yet by browser software.

HTML

HTML Introduction

Learning HTML is the first step to mastering the web. HTML stands for Hypertext Markup Language, which is the markup structure for web pages. When browser software accesses a file it understands how to parse the document according to the file's extension.(.html - .txt - .php - .xml - .pdf - .doc - etc... ). HTML provides us a means of laying out and structuring our web pages using paragraphs, graphics, images, audio/video media, applications, forms, user interaction and much more.

As it is with a few other open source web technologies that this website covers, HTML is maintained by the people of W3C. All web masters owe gratitude to the Consortium for enhancing the things we can do on our web pages and how we can interact with our users.

When browser software reads an HTML document it interprets exactly how to render it from the HTML tags and elements laid out in it. An HTML document is just a well dressed text(.txt) file, given a different extension(.html) so browser software can communicate with it the way it needs to.

HTML uses elements that have tags that wrap around your content and this is what tells the browser software how to treat that particular element and all of the content in it. Mastering HTML requires mastering the elements, attributes and event handling of the elements(aka: "tags"). It is key to know all of the elements at your disposal, this way you can choose the correct elements and avoid using elements out of the context for which they are specified.