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Showing posts with label Education. Show all posts
Showing posts with label Education. Show all posts

What is Search Engine Optimization? Search Engine Glossary for superior understanding about SEO


What is Search Engine Optimization? Search Engine Glossary for superior understanding about SEO

Search-Engine-Optimization (SEO) Search-Engine-Optimization (SEO)[/caption]

What is Search Engine Optimization

Search engine optimization (SEO) is the exercise of growing the amount and superiority of traffic to website through organic search engine results. Search engine optimization is exactly how it sounds: optimizing your website’s content for search engines. That way Google (and other search engines) can easily index your content, categorize each of your pages based on the information they contain, and then serve those pages up to people who are looking for that information on the Internet.

How Search Engines Works

A search engine’s main process is threefold: crawling, indexing, and querying. Let’s define each.
  • Crawling: A search engine runs a software program called a “spider” to discover content on the web.
  • Indexing: The search engine analyzes the content it finds to determine what it’s about, then indexes it–or organizes the content–so that it’s quickly retrieved when the next step occurs.
  • Querying: When you conduct a search online, the search engine fetches a list of results for you to consider. These search results appear on a SERP, or a Search Engine Results Page. As Google puts it, “…our algorithms look up your search terms in the index to find the appropriate pages.”

To recognize what SEO actually means, let's check below:

  • Quality of traffic. You can attract all the visitors in the world, but if they're coming to your site because Google tells them you're a resource for WordPress Tips when really your website providing WordPress Tips information, that is not quality traffic. Instead you want to attract visitors who are genuinely interested in products that you offer by SERP.
  • Quantity of traffic. Once you have the right people clicking through from those search engine results pages (SERPs), more traffic is superior.
  • Organic results. Ads make up an important part of many SERPs. Organic traffic is any traffic that you don't have to pay for.

In This post which is about Search Engine Glossary will help you enhanced understand some of the terms normally used in the SEO industry.


  • 404 Error Page
The web page that displays when a user tries to view a page that no longer exists or the page file name has changed.
  • Bounce rate
The percentage of visitors to a particular website who navigate away from the site after viewing only one page
  • Abandonment Rates
Percentage of site visitors who view a page and then exit without linking to other pages on the site.
  • Alt tags
More correctly, these are ALT “attributes” (e.g. IMG is a “tag”). This is text coded in the HTML that associates words with web graphics.
  • Back Links
The number of links pointing to a website, “link popularity”.
  • Cache
Web content saved by the search engines in their indexes.
  • Call-To-Action
A way to engage the website visitor that encourages them to interact with the company.
  • Cloaking
At the same URL (web address) showing one page to a search engine spider and a different page to a human visitor. Frowned upon by search engines as deceptive, sites may be severely penalized by the engines if they use cloaking.
  • Crawler-based search engines
Engines that use automated software to index the billions of files online.
  • Conversion
When a website visitor takes a desired action, such as a sale or downloads a file.
  • CTR (Click through Rate)
Percentage of users who click an online ad after viewing it.
  • Directories
Websites that list other sites by category, e.g. Yahoo! Directory. Historically, directories typically listed entries on people or businesses, and their contact information; such directories are still in use today. A web directory includes entries about websites, including links to those websites, organized into categories and subcategories.
  • Flash
Macromedia software that creates vector-based graphic animations with small file sizes for use online.
  • Framed site
Using a specific type of HTML code that places “pages inside pages”. Has significant disadvantages and a few advantages.
  • H1, H2, H3, H4, H5 tags
In HTML, the code used to define a page title or subhead.
  • HTML Text
Text on a web page that is created using HTML (which can be indexed by the engines) as opposed to a graphic (which cannot).
  • Hyperlinks
A link from one web page to another (links can also point to another location on the same page).
  • Website Indexing 
Online content that the search engines can index. Some website contents are not indexing by(e.g. locked PDF files, text in a graphic, Robots.txt Blocking).
  • JavaScript
A programming script used on websites.
  • Keyword Stemming
Keyword stemming is a useful tool for web pages and search engine optimization. The process of keyword stemming involves taking a basic but popular keywords to a particular website and adding a prefix, suffix, or pluralization to make the keyword into a new word. Google searches not only for your search terms, but also for words that are similar to some or all of those terms, including plurals.
  • Link Popularity
The number of links pointing to a website.Link popularity refers to the number of Backlinks (incoming links) that point to a given website. Link popularity is a term that refers to how many other links point towards a particular website. The term link popularity also has two different forms, Internal and External, which refer to the links coming from the websites own web pages and from other websites. Internal link popularity means the number of links to the website from web pages that belong to the particular website. External link popularity is the number of links from outside sources that lead back to the particular website. In the end, websites with high link popularity have what is called link superiority and have a reputation for being informative, as well as ranking highly on search engines. Link popularity is also an approach that many search engines take when deciding where to rank websites.
  • Meta Description
HTML code that contains a descriptive sentence or two about the web page.The meta description is a ~160 character snippet, a tag in HTML, that summarizes a page's content. Search engines show the meta description in search results mostly when the searched for phrase is contained in the description. Optimizing the meta description is a very important aspect of on-page SEO.
  • Natural Listings
That part of the search engine results that is not paid for, typically in the central area of the results page.
  • Off-The-Page
Factors considered by the search engines when ranking a page that are not part of the web page, e.g. back links.
  • On-The-Page
Factors considered by the search engines when ranking a page that are part of the web page, e.g. text content, title text, etc.
  • Organic Listings
Organic search results are listings on search engine results pages that appear because of their relevance to the search terms, as opposed to their being advertisements. In contrast, non-organic search results may include pay per click advertising.
  • Page Rank
Devised by Google, it measures not only how many links point to a website, but the “quality” of the sites providing the links.
  • Page Views
The number of requests to view a specific web page in a specific time frame (the same person could make multiple requests).
  • Paid Inclusion
Paying money to be listed in a search engine or online directory. Paid inclusion is a search engine marketing product where the search engine company charges fees related to inclusion of websites in their search index. The use of paid inclusion is controversial and paid inclusion's popularity has decreased over time among search engines.
  • Paid Placement
Paying money to have an advertisement shown on a search engine results page. Paid placement is a program in which advertisers' listings are guaranteed to appear on a Results Page when particular Keywords are searched. The ranking of paid placement listings is determined by competitive bidding.
  • Phrase Match
Performing a search with quotation marks around the phrase so that the search results will show web pages with the exact phrase.
  • Pop-up Ads
A form of online advertising that opens a new web browser window to display advertisements.
  • PPC “Pay per Click”
Paying a small amount each time a user clicks on an online ad.
  • Redirect
A file on the server indicating that the requested page has permanently (301) or temporarily (302) been moved to another location.
  • Robots.txt
A text file that instructs the search engines about pages or directories to exclude from its database.
  • ROI “Return on Investment”
How much revenue is generated compared to how much was spent on a marketing campaign
  • Search Engine Marketing (SEM)
The practice of marketing and advertising through the search engines.
  • Search Engine Optimization (SEO)
Designing a website so that it ranks highly in the search engines when someone searches for specific phrases related to the site.
  • Search Engine Rankings
The position a site has on a search results page when a specific phrase is searched for.
  • Search Engine Referrals
Visitors who arrive at a website after clicking a link on a search engine results page.
  • Search Engine Results Page (SERP)
The page that displays in a search engine when a specific phrase is searched for.
  • Search Term
The word or words entered by the user into the search engine.
  • Similar Pages
Identifies sites that the search engines think are the same theme.
  • Title Tag
In HTML, an area where text is placed that shows at the very top of the browser window. Search engines consider this area critical.
  • Unique Visitors
The number of individuals who visit a website during a specific time (the same person visiting twice is only counted once).
  • Web Spider
Software that browses the Web in an automated manner and keeps a copy of visited pages in its database. Also known also as a crawler.
  • Webinar
Online seminar that may contain audio and video.
  • Search Engine Saturation
The number of web pages that a search engine has indexed from your website.
  • Search Engines
A system designed to make searching the web easier. The searcher types in a query and this results in a page is full of various relevant media types (text, imagery, video, etc.). Popular examples include Google, Bing and Yahoo.
  • Algorithm
The procedures or formulas that establish computer programs. Examples = search engines use algorithms to find the right results for a search query. An image editing program would use an algorithm to process the image’s data.
  • Bing
The search engine developed by Microsoft. It provides a basic web search, as well as a more focused search around categories such as images, shopping, news, maps, etc.
  • PageRank
Google’s ranking software that determines how relevant a web page is based on a search query. It calculates both the number of incoming links and the quality of these links.
  • SEO: Search Engine Optimization
The process of getting on the results page from a search query through free/organic means. This includes producing quality content and incorporating long-tail keywords in effective ways.
  • Black Hat SEO
More aggressive methods of optimization that focus on taking advantage of the more technical side of searching rather than focusing on user behavior. This goes against what SEO is intended to do and can cause your site to be penalized. Examples = keyword stuffing, Hidden text, doorway pages. (Doorway pages are web pages that are created for spamming. This is for spamming the index of a search engine by inserting results for particular phrases with the purpose of sending visitors to a different page.)
  • Keyword
A word or phrase which has been identified as the one that people would use when searching for that subject matter in the search query. There are ways to optimize keywords such as through SEO
  • Keyword Stuffing
The method of filling a web page with numerous keywords in order to rank higher on a search results page. Doing this make the words appear unnatural since they aren’t necessarily appropriate in the phrase when overused. This is considered an ineffective SEO tactic and Google now punishes a website through lowering their ranking if the algorithm detects this practice.
  • Long-Tail Keywords
Phrases, usually three to four words that are most pertinent to what is being sold. These are identified by analyzing what a searcher might type in their search query if they were looking for a specific product or service.
  • Local Search
Using geographic areas as a factor in search engine results so that the product or service comes from a certain location in regards to the user.

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What is windows operating system and Types of Windows OS

What is windows operating system and Types of Windows OS

What is windows operating system and Types of Windows OS

Windows is an operating system designed by Microsoft. The operating system is what permits you to use a computer. Windows comes preloaded on most new personal computers (PCs), which helps to make it the most popular operating system in the world. You can also install windows manually in your computer.

Windows makes it possible to complete all types of everyday tasks on your computer. For example, you can use Windows to browse the Internet, check your email, edit digital photos, listen to music, Create Project reports, play games, and do much more.

Windows is also used in many offices because it gives you access to productivity tools such as calendars, word processors, and spreadsheets.

Microsoft released the first version of Windows in the mid-1980s. There have been many versions of Windows since then, but the most recent ones include Windows 10 (released in 2015), Windows 8 (2012), Windows 7 (2009), Windows Vista (2007), and Windows XP (2001).

List of Windows Client OS with their Version Numbers



Operating System

Version Number

Windows 1.0
1.04
Windows 2.0
2.11
Windows 3.0
3
Windows NT 3.1
3.10.528
Windows for Workgroups 3.11
3.11
Windows NT Workstation 3.5
3.5.807
Windows NT Workstation 3.51
3.51.1057
Windows 95
4.0.950
Windows NT Workstation 4.0
4.0.1381
Windows 98
4.1.1998
Windows 98 Second Edition
4.1.2222
Windows Me
4.90.3000
Windows 2000 Professional
5.0.2195
Windows XP
5.1.2600
Windows Vista
6.0.6000
Windows 7
6.1.7600
Windows 8.1
6.3.9600
Windows 10
10.0.10240

Different Types of Windows Operating Systems


Computer users have differing requirements. While a distinctive business needs to manage network permissions and give many users concurrent access to shared resources, a home user may simply use his computer to check email and play an random games. Microsoft markets several versions of Windows to serve the needs of these markets. Each edition has a different price point and feature set from the others.

Home Computers

Home editions of Windows such as Windows 7 Starter and Windows 7 Home Premium or Windows 10 provide the basic functionality that personal computers require. These include the ability to run software, play games, access the Internet and view or manipulate media such as music, videos and images. To keep consumers' costs down, these editions of Windows do not include some of the advanced features that business users require.

Business Computers

Business computers often require features not needed on standard home machines. For example, Windows 7 Professional or ultimate editions includes a feature called "Windows XP Mode" for running legacy software. It also includes the ability to act as a host for the Remote Desktop application and has a self-encrypting file system to prevent data loss from theft. Windows 7 Enterprise features data encryption for removable storage devices. It also has the ability to run on a computer with no hard drive by booting from a virtual image hosted on a server.

Servers Computer

Business networks may have many users logged in to their computers concurrently during the working day. Each user needs to access resources such as databases, intranet websites, email, Sharing files and Internet gateways. In addition, each user has her own password and access permissions. The powerful computer needed to manage network access for a large user base is called a server. Because servers perform very different roles from standard business computers, they require different operating systems. The Windows Server product line is Microsoft's offering for servers.


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What is Cache Memory. Types and functions of cache memory?

What is Cache Memory. Types and functions of cache memory?

Cache Memory

Cache Memory

The Cache Memory is the Memory which is very near to the central processing unit , all the Fresh Commands are Stored into the Cache Memory. The Cache Memory is committed for storing the input which is given by the user and which is essential for the CPU to Implement a Task. But the Capacity of the Cache Memory is too small in compare to Memory and Hard Disk.

Prominence of Cache memory

The cache memory lies in the path between the processor and the memory. The cache memory consequently, has lesser access time than memory and is faster than the main memory. A cache memory have an access time of 100ns, while the main memory may have an access time of 700ns.

The cache memory is very expensive and hence is limited in capacity. Earlier cache memories were available separately but the microprocessors contain the cache memory on the chip itself.

The need for the cache memory is due to the mismatch between the speeds of the main memory and the CPU. The CPU clock as discussed earlier is very fast, whereas the main memory access time is comparatively slower. Hence, no matter how fast the processor is, the processing speed depends more on the speed of the main memory (the strength of a chain is the strength of its weakest link). It is because of this reason that a cache memory having access time closer to the processor speed is introduced. 

The cache memory stores the program (or its part) currently being executed or which may be executed within a short period of time. The cache memory also stores temporary data that the CPU may frequently require for manipulation.

The cache memory works according to various algorithms, which decide what information it has to store. These algorithms work out the probability to decide which data would be most frequently needed. This probability is worked out on the basis of past observations.

It acts as a high speed buffer between CPU and main memory and is used to temporary store very active data and action during processing since the cache memory is faster than main memory, the processing speed is increased by making the data and instructions needed in current processing available in cache.
types of cache memory

A computer can have different levels and sizes of cache depending on the CPU architecture. The most common levels of cache are L1 and L2 cache, where L1 is closest to the Cpu and hence its access time is much faster compared to L2 cache , the sizes of these caches can vary from 8Kb - 128kb or even 256Kb in modern systems.

Another mode of caching is Disk Caching

Disk caching works under the same principle as memory caching, but instead of using high-speed SRAM, a it uses conventional main memory. The most recently accessed data from the hard drive (as well as adjacent sectors) is saved in a memory buffer. When a program needs to access data from the disk, it first checks the disk cache to see if the data is there. Disk caching can dramatically improve the performance of software. Because accessing a byte of data in RAM can be thousands of times faster than accessing a byte on a hard disk.

The effectiveness of any cache is determined by its hit rate. The higher the hit rate the better the performance of cpu and the better the caching algorithm implemented.

Two most common algorithm for caching are

· Least Frequently Used (LFU): This cache algorithm uses a counter to keep track of how often an entry is accessed.
· Least Recently Used (LRU): This cache algorithm keeps recently used items near the top of cache.

Recall: A lower size cache with high hit ratio, is far better than a large size cache with poor hit ratio. 

A CPU cache is a cache used by the central processing unit (CPU) of a computer to reduce the average time to access data from the main memory. The cache is a smaller, faster memory which stores copies of the data from frequently used main memory locations. Most CPUs have different independent caches, including instruction and data caches, where the data cache is usually organized as a hierarchy of more cache levels (L1, L2, etc.). 

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What is Difference Between Pixel and Resolution

What is Difference Between Pixel and Resolution

Resolution Vs Pixel Density in Displays

Pixel vs Resolution

Summary: Difference Between Pixel and Resolution is that pixel is the smallest element in an electronic image. The greater the number of pixels the camera uses to capture a picture, the better the quality of the picture. While Resolution is the number of horizontal and vertical pixels in a display device. A digital camera’s resolution is defined in pixels.

Pixel

A pixel (short for picture element) is the smallest element in an electronic image. The greater the number of pixels the camera uses to capture a picture, the better the quality of the picture. Digital camera resolutions range from about 4 million to more than 16 million pixels (MP).
Usually displays are measured in size(in centimeters and inches). Here we only measure the diagonal size and not the horizontal or vertical size of the screen. There is also another important property of display which is the resolution. Resolution refers to size of the display in terms of pixels. E.g. Resolution of 800×600 pixels means that the there are 800 pixels horizontally and 600 pixels vertically. So therefore there are a total of 480000 pixel in the display.
Pixel is just an element of the picture that plays an important role to complete the image. The word ‘pixel’ was first published by Frederic C. Billingsley in 1965. The measurement of the screen can be described through pixels. Hence, the size of the image also depends on the number of pixels, the larger the number of pixels your image is having the greater the size will be.

Pixel Density


Many of us are not aware of the importance of Pixel Density in displays. It is the thing which describes the sharpness and clarity. Pixel Density is usually measured in PPI (Pixels Per Inch) which refers to number of pixels present per inch on the display. Higher the pixel density higher is the sharpness of the content. Pixel Density is calculated based on the resolution and size of the display.
Pixel Density= Root((Horizontal Number of Pixel^2) + (Vertical Number of Pixel^2))/Screen Size

Resolution

One factor that affects the quality of digital camera photos is its resolution. Resolution is the number of horizontal and vertical pixels in a display device. A digital camera’s resolution is defined in pixels. Resolution is made up of all the elements (pixels) combined together to form a quality image. The greater the resolution is the better you will get the quality of your picture. Resolution describes the elements or pixels in an image. You can measure resolution in three difference ways, Sample per inch (spi, scanners) or Pixel per inch (ppi, monitors) or Dots per inch (dpi, printers).

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Job Profile: Careers in IT : System administrator

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System administration refers to the management of one or more hardware and software systems.

The task is performed by a system administrator who monitors system health, monitors and allocates system resources like disk space, performs backups, provides user access, manages user accounts, monitors system security and performs many other functions.

 
System administrator

Duties of a system administrator

The duties of a system administrator are wide-ranging, and vary widely from one organization to another. Sysadmins are usually charged with installing, supporting, and maintaining servers or other computer systems, and planning for and responding to service outages and other problems. Other duties may include scripting or light programming, project management for systems-related projects.

The system administrator is responsible for following things:

  1. User administration (setup and maintaining account)
  2. Maintaining system
  3. Verify that peripherals are working properly
  4. Quickly arrange repair for hardware in occasion of hardware failure
  5. Monitor system performance
  6. Create file systems
  7. Install software
  8. Create a backup and recover policy
  9. Monitor network communication
  10. Update system as soon as new version of OS and application software comes out
  11. Implement the policies for the use of the computer system and network
  12. Setup security policies for users. A sysadmin must have a strong grasp of computer security (e.g. firewalls and intrusion detection systems)
  13. Documentation in form of internal wiki
  14. Password and identity management

Cloud computing and sysadmin

Cloud computing is nothing but a large number of computers connected through the Internet/Wan. Cloud computing is now part of technology and sysadmin must lean:
  1. Automation software such as puppet, chef, etc.
  2. Cloud infrastructure such as AWS, Openstack etc.
  3. Network services in cloud such as Content delivery networks (Akamai, CloudFront etc) and DNS servers.
  4. Source control
  5. Designing best practices for backups, and whole infrastructure.

What is so special about the system administrator account?

The root account has full (unrestricted) access, so he/she can do anything with system. For example, root can remove critical system files. In addition, there is no way you can recover file except using tape backup or disk based backup systems.
Many tasks for system administration can be automated using Perl/Python or shell scripts. For example:
  • Create new users
  • Resetting user passwords
  • Lock/unlock user accounts
  • Monitor server security
  • Monitor special services etc

Most important skill to a system administrator

Problem solving, period. This can some time lead into all sorts of constraints and stress. When workstation or server goes down, you are called to solve the problem. You should able to quickly and correctly diagnose the problem. You must figure out what is wrong and how best it can be fixed in small amount of time.

Job Summary

Responsible for the technical design, planning, implementation, and the highest level of performance tuning and recovery procedures for mission critical enterprise systems. Serves as a technical expert in the area of system administration for complex operating systems. Recommends the redesign and configuration of operating systems and system applications. Investigates and analyzes feasibility of system requirements and develops system specifications. Identifies methods, solutions, and provides project leadership and management in order to provide a high level of service to the customers of the department. Performs full supervision of Operations staff.


Typical Duties and Responsibilities

1. Manages the day-to-day operations of the PCC host computers by monitoring system performance, configuration, maintenance and repair. Ensures that records of system downtime and equipment inventory are properly maintained. Applies revisions to host system firmware and software. Works with vendors to assist support activities.
2. Develops new system and application implementation plans, custom scripts and testing procedures to ensure operational reliability. Trains technical staff in how to use new software and hardware developed and/or acquired.
3. Supervises Operations staff including hiring, training, evaluating and disciplining. May guide or provide work direction to technical staff, contract staff and/or student employees. Determines appropriate coverage for all hours of operation.
4. Performs troubleshooting as required. As such, leads problem-solving efforts often involving outside vendors and other support personnel and/or organizations.
5. Establishes, maintains and manages users Unix accounts. Installs, modifies and maintains systems and utility software on server computer systems. Provides server support related to other software.
6. Establishes guidelines and methods for the installation and management of the host computer operating systems, disk arrays, fiber channel switches, tape libraries and other components.
7. Ensures high availability and acceptable levels of performance of mission critical host computer resources.
8. Develops procedures to maintain security and protect systems from unauthorized use, acts of nature and user abuse.
9. Develops procedures, programs and documentation for backup and restoration of host operating systems and host-based applications.
10. Develops and coordinates project directions and schedules to maximize benefits and minimize impacts on the customer organizations. Provides leadership in planning and implementation of projects for computer operations and enterprise systems administration.
11. Develops tools, procedures, and training sessions for Operations, Client Support and Systems Development staff to assist with work.
12. Manages the data center and computer host systems including hardware, software and equipment such as air-conditioning system, UPS (uninterrupted power system) and fire protection system.
13. Stays current with technological developments in systems administration technology and recommends ways for PCC to take advantage of new technology.
Positions in this classification may perform all or some of the responsibilities above and all positions perform other related duties as assigned.


Minimum Qualifications

Associate's degree in Computer Science or related discipline. Relevant experience may substitute for the degree requirement on a year for year basis. Three years work experience in complex systems design, programming and systems software and support.

Knowledge of: Programming languages and operating systems; current equipment and technologies in use; Unix system administration, enterprise backup and recovery procedures, and system performance monitoring tools; effective project management techniques; principles and practices of effective management and supervision.

Ability to: Plan, organize and document complex system design activities and to configure systems to be consistent with institutional policies/procedures; communicate technical/complex information both verbally and in writing; establish and maintain cooperation, understanding, trust and credibility; perform multiple tasks concurrently and respond to emergency situations effectively.


Work Environment and Physical Requirements

Work environment includes typical computer related noise levels and paper and equipment generated dust. Exposure to video display terminals occurs on a regular basis. Incumbent is on call to provide support services during off hours. Scheduled night and weekend work is required. Learned physical skill is required for keyboarding and use of peripheral equipment. Moderate lifting.

There are different types of system administrators based on their roles and responsibilities. A bigger company might have different system administrators having different roles, but for smaller company, most of the different roles might be shared by just a few system administrators, or even one single person. Some of the different types of system administrators are:

  • Server administrator – maintains the operating system of the servers, and to some extent, the applications as well, such as the mail services, the web services, etc. He is also in-charge of troubleshooting any hardware, operating system or application related problems.
  • Network administrator – maintains the network infrastructure, such as the routers and switches, and troubleshoot network-related problems.
    • Database administrator (DBA) – maintains the database system used by organisation. In bigger organisation which uses bigger and more complex databases, there is a DBA which specifically responsible for this role. In smaller organisation, this role would normally be shared by the server administrator
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How does WhatsApp technology works?

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Whats App is Chat application. WhatsApp is a texting service between mobile phones as a replacement for the regular SMS text messages. Over millions users are active worldwide using the Whatsapp service. Whatsapp uses an internet connection between phones. The service is available for iPhone, Blackberry, Android and Nokia Symbian60-phones.

How does WhatsApp technology works?
The major difference between regular SMS text messages and Whatsapp text messages is that Whatsapp is free: You use the internet connection on your phone (wifi or part of you mobile data package depending on subscription or pre paid type).

We call them Instant Messaging.  This means the messaging between sender and receive should happen in real time, unlike email (offline).

So you need to first understand challenge here to understand how chat apps work.  If you store something on database, then you pass again to another user, it becomes offline (not in real time).  If you pass any message and it stores and also pass at same to other user, it becomes IM (Instant messaging). 

Now in development, there are different PROTOCOLS that help achieve things.

For Emails its: SMTP, POP3 etc.
For Chat its: XMPP (Extensible Messaging and Presence Protocol)

It is protocol based on another format named XML (like html, not exactly, but to give you idea).  Using XMPP protocol, XML as communication medium and setting up this on a server, that host it and helps pass all communication and also setup logic on this server (Basically coding).  So there are many server created with protocol XMPP like eJabber.

Interestingly, WhatsApp is related to "Yowsup" , a Python library.  Python is a programming language on which Quora, YouTube etc. are built! You can find this Yowsup library on tgalal/yowsup.

So now lets put together all above information.
A user A has internet and a client application (whats app) installed on say Android phone), A user B has internet and has same client application (Whatsapp) installed on his iPhone. (So basically cross platform).

A types message "Hi" to B.  The message is passed via Web Services to XMPP server, The XMPP server has list of all WhatsApp user, based on unique phone number, it will detect B and XMPP server will then send message "Hi" to B with web service.  B will recieve this message on iPhone.  In between there will coding done with business rules on server, database level and on client applications as well. 

Whatsapp is implemented at server end over the protocol XMPP. Exactly it is done on XMPP lite which is well established open source chat engine. 

XMPP (Extensible Messaging and Presence Protocol)
What is the Technology behind WhatsApp?
WhatsApp uses a customized version of the open standard Extensible Messaging and Presence Protocol (XMPP) upon installation. WhatsApp automatically compares all the phone numbers from the device's address book with its central database of WhatsApp users to automatically compares all the phone numbers from the devices address book with its central database of WhatsApp users to automatically add contacts to the users WhatsApp contact list.

XMPP

What is Extendible Messaging and Presence Protocol (XMPP) ?
The Extensible Messaging and Presence Protocol (XMPP) is an application profile of the Extensible Markup Language (XML) for streaming XML data in close to real time between any two or more network-aware entities. The address format for XMPP entities was originally developed in the Jabber Open Source Community in 1999. It functions between or among servers, and facilitates near-real-time operation. The Protocol may eventually allow internet users to send instant messages to anyone else on the Internet, regardless of differences in Operating systems and browsers. 

XMPP is sometimes called the Jabber protocol, but this is a technical misnomer. Jabber, an IM application similar to ICQ (I Seek You) and others, is based on XMPP, but there are many applications besides Jabber that are supported by XMPP. The IEEE XMPP working group, a consortium of engineers and programmers, is adapting XMPP for use as an Internet Engineering Task Force (IETF) technology. 

In addition, the Messaging and Presence Interoperability Consortium (MPIC) is considering XMPP as an important interoperability technology. Eventually, XMPP is expected to support IM applications with authentication, access control, a high measure of privacy, hop-by-hop encryption, end-to-end encryption, and compatibility with other protocols.


Database management
For the database management Mnesia DB comes into play. Mnesia is a multiuser distributed DBMS which happens to be the default DB of ERLANG. Thus by using Mnesia, the app is able to achieve quicker request responses, thereby improving the overall efficiency.

FreeBSD is the operating system upon which WhatsApp is laid upon. Improvising on the ERLANG based applications and optimizing FreeBSD, WhatsApp is able to achieve better throughput. For storing multimedia files, the app uses an exclusive web server YAWS.
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Best Mobile Apps to Boost Productivity

Productivity is so much more than a buzzword for freelancers and project co-coordinators alike. Staying productive can sometimes be harder to achieve than it should, especially when working in a busy office. With no boss looking over your shoulder you need to keep your eye on the ball to stay on track and meet your targets and deadlines.

 
Mobile Apps
If you are new to working from home, you probably haven’t noticed your apartment looks a lot cleaner these days. And you now know all the best before dates for your fridge items. You have made a complete turnaround in your day to day schedule, so staying focused on not letting your standard of work drop is now your number one priority.

The good news is that, as a freelancer, you now have a whole army of mobile apps ready and waiting for your requirements. You need to take heed and find the ones that will work best for you as soon as possible. The new generations of mobile apps are all better individually than all the systems you used for your Filofax, and the days of spreadsheets being used as organisers are over. It is time to discover just how good the latest raft of apps is. After all, it’s all about keeping up with your productivity and getting help is always a reasonable option.

Any.Do-Mobile-App
Any.do is a good looking task manager with a difference. The big plus is a unique tool every morning to take you through your everyday tasks, so you don’t forget all your important tasks and meetings for the day. This friendly nudge every morning is called the Any.do Moment. You will get familiar with it until completely relying on it every morning like the assistant it has been designed as. 
The Any.do is a collaborative effort and presents a beautifully laid out utility available for Android and iOS.

Abukai Expenses will make tedious expense reports a thing of the past. Your organisation would do well to employ this easy integration system for expense filing. Abukai Expenses works for both Android and iOS and has customisation laid on for many of the back-end financial software products. The app allows you to snap receipts on the go and feed them to your accounting system, so no information is lost.

This is an excellent free app for time tracking. Rescue Time tracks how you spend your time and which apps you keep going back to use most. On analysis, you can ascertain everywhere you waste time and where you could be more productive. There are graphs and chart presentation of data to indicate where you need to change your ways. Writers, for instance, may be unaware they spend too much time on research than honing their writing skills. Rescue Time is a fascinating Android app for management.

Social media freelancers should know about the buffer app. Buffer schedules all your social media posts to be done together. You can plan to put out your messages collectively for your Facebook posts, Google Plus posts, tweets, and LinkedIn posts. With one click you can update your aggregate work output simultaneously. Buffer is particularly useful for professional tweeters who need to co-ordinate better the timing of their tweets to stay timely and relevant. 
With increasing importance dependant on content, for the areas like digital marketing, sharing and link-building appropriate control will help efficiency. Download it on your Android or iOS smartphone.

Productivity apps are featuring workplace collaborative tools more and more, and it is easy to see why. A large part of management now requires for more teamwork and employees working together, so communicating frequently and unimpeded with an app such as Asana should be warmly welcomed. Asana has been successfully designed to keep teams working together with complete accountability for who-did-what in real time. 
All businesses whatever size can get their team members away from slow and inefficient emailing to close team collaboration. Get the updated version on your Android phone.

Task management has just been made simple by an app called Remember the Milk. Apart from the cool name, RTM doesn’t lack any functionality and will become a vital source of note sorting for you quicker than you think. It is web based but supports Android and iOS for mobiles. RTM will integrate effectively with Evernote, MS Outlook, Gmail, Google Calendar and Twitter. The useful user interface comes with keyboard shortcuts to make task management that little bit quicker.

Nutcache is perfect for online invoicing. It is simple, fast and offers multi-lingual capabilities. Invoice and estimates are free including time tracking. For hour-logging per jobs,  Nutcache also handles client billing and the available mobile time logging app for logging hours anywhere all done through iOS or Android.  
Even the free version includes loads of great features such as accessibility to 20 comprehensive and flexible reports for real-time business analysis of activity. NutCache keeps some sophisticated billable hours tools at a comfortable and convenient central location. Freelancers and team collaborators can pitch in some brainstorming time or use the tools to boost productivity and project building at the same time.

Brewster is an all-in-one contacts app that effortlessly pulls in all your places of contact information and provides you with a go-to logical place for that vital information. Any duplicates across the applications are handled without fuss and contact info is keep up to date across-the-board. Brewster in Android proves to be a huge time saver whenever you are working with networking back up.

Trello makes creativity accessible to whatever project you are working on. The popular app that is available on both Android and iOS operating system uses a card system to hold all the relevant bite-sized information that is linked to a larger project and is open to inviting collaborators to work on the project. This access can be revoked at any time, or the cards are also meant to a private project. The card system makes productivity accessible for task completion one by one while all your progress keeps the bigger picture up to date on a larger white board.

LastPass is perfect for anyone who gets frustrated by being prompted for passwords all the time. LastPass suggests you keep one final password with them so you can never get blocked from important work when forgetting your latest password update. LastPass is great news for those who don’t want to keep all their memory joggers strewn across a myriad of sticky notes and secret files. 
Download free on both Android and iOS platforms.
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