Mail Server Or E-Mail Server

A mail server respond to requests for delivery of electronic messages. The server stores the messages arrive, and transmits the messages going to the recipient (another mail server). A mail server respond to claims handling and recovery of stored messages.

SMTP is a protocol used to route e-mail between a client and server, as well as a server and another server. POP is a protocol used to retrieve messages and forward them to the client. IMAP is a protocol used to examine and manipulate messages from a client.

Leaving messages are often placed in queues, bundled and sent at regular intervals. see spooling

A WebMail application is placed on a web server, which acts as a client on a mail server.

Web server Or HTTP Server

A web server responds to requests for documents such as the World Wide Web. Each passage of a hypertext document to another through path of a hyperlink in the client software (most often a browser) causes the sending of a new application. Each request can be sent to a different server.

In response to a request, the server can send a document that is stored as a file in the mass memory of the server, or run a treatment and then send the result as a document. HTTP and HTTPS protocols are web servers.

Apache is a web server for UNIX operating systems and Windows. Internet Information Services (IIS Short) is a web server included in Windows operating systems.

A web application is a program consisting of a combination of treatments that create instant documents following receipt of requests for consultation. WebMail, Wiki, Weblog and web applications are.

Game Server

The game server is part of a game software for online multiplayer client-server architecture. It responds to requests for distribution of operations performed by each player. The server validates the operations of each player - referee the game, and then forward the developments of the game to other players.

The game server stores the state of the game in memory, and maintains. A copy of the state of the game is sent to any player when he entered the game then the game client software maintains its own copy of the state of play.

Upon receipt of an application - operation performed by a player - the server performs various treatments in order to monitor compliance of the operation by the rules of the game then it makes the necessary changes on the state of the game that it stores in memory. The server then sends to the clients list of changes made on the state of the game and then each client maintains its own copy of the state of play.

The protocol is different for each online game. It depends on the speed in an action game like Quake or Half-Life protocol is adapted to a fast evolution.

OS (Operating System) Of The Server

There are many operating system (OS) optimized for server work, particularly in families Unix and Windows NT.

In these operating systems the emphasis is on information security, especially confidentiality and availability, as well as the ability to perform many treatments simultaneously. The man-machine interface is often poorly developed, the servers are rarely handled.

In the server operating system, a kernel provides preemptive multitasking execution of multiple treatments. Each process is executed in a confined space (also called, sandbox) so that the crash or unexpected behavior of this process will not affect other processes.

To ensure confidentiality, each process is attached to a user account (typically the user who initiated the request), and each transaction is subject to an access control mechanism which will allow or deny based Information permissions, access control lists or privileges.

The servers being used in the network, the operating system is equipped with various softwares that are to be used with many protocols, and can be used as a relay or routing. Various such server softwares are included in the operating system.

Servers are often used to store large amounts of data. The operating system can perform automatically tasks in batch on a regular routine. These are typical tasks of backup or archiving data.

In a minor man-machine interface of a server operating system is poorly developed, and multimedia capabilities are reduced - the machines often do not have sound card. The X Window System is a software man-machine interface in client-server architecture included in almost all Unix operating systems.

Server Software

Is called server software that deals with requests sent via a network. The launch and implementation of software is done without human intervention, it may take place when you start the computer, i.e., boot the computer, or upon request. Nothing is displayed on the screen and the software is invisible. See also daemon.

Server software can co-operate with any client that uses the same protocol. Similarly a client may co-operate with any server on the same protocol.

File Server

A file server responds to requests for the creation, moving, deleting, reading, modification or blocking of a file. Files are stored in mass storage server - mostly from hard drives, and handled according to the demands of customers.

File servers are often included in operating systems. CIFS is the protocol of the file server and printing included in Windows operating systems. NFS is a protocol common file server for UNIX operating systems. Samba is a server CIFS protocol for UNIX operating systems. FTP is a protocol for file server used on the Internet.

A NAS is a hardware / software turnkey provided exclusively for use as file server. SINs recognize several protocols..

Print Server

A print server responds to requests relevant to the work of digital printing. Documents are placed in queues and then sent to printers. see spooling.

Applications involve manipulating queues (one for each printer): reading the content, addition or deletion of documents, call waiting, priorities. The server automatically sends the documents one after another to the printer. Documents may undergo changes in format in order to adapt to the characteristics of the destination printer. PCL and PostScript are common data formats in digital printing.

CIFS is the protocol print servers and files included in Windows operating systems. CUPS is a print server running on the Unix operating systems.

Database Server

A database server responds to requests for manipulating data stored in one or several databases. This is typical of applications for searching, sorting, addition, alteration or deletion of data.

The database server is part of a management system database (abbreviated DBMS) - software that manipulates a database - which includes a client and server software. Requests for data manipulation are often created by management software in the form of SQL queries, and then the client transmits to the server using a protocol specific to the DBMS.

Oracle, Microsoft SQL Server or MySQL are SGBD which include a database server.

An application in three-tier architecture typically includes a server database (Tier 3) with a web server (Tier 2) and a web browser (Tier 1). The application hosted by the web server is the client server database.

Continued…

Uses Of The Server

The main uses of a server are:

* File Server: File Server is used for storing and sharing files. The files placed in the mass storage server can be handled simultaneously by multiple clients.

* Print Server: Server is used as an intermediary between a set of customers, and a set of printers. Each client can send documents to print to a printer connected to the server.

* Database Server: Server is used to store and manipulate data contained in one or more databases and shared among several clients. Databases can be flat structure databases (non-relational database management system — DBMS), or can be relational database management system (RDBMS), the latter is being used widely by almost all large-scale companies and multinationals for the database needs.

* Mail server: the server is used to store and transmit electronic mail. The outgoing mail server is transmitted to the recipient. The courier arrived is stored on the server and is accessible by the client.

* Web server: the server stores and manipulates the pages of a website, and on request to the client.

* Game Server: also called the referee server, it follows the evolution of a game and brings together the various players in the multiplayer online games.

* Application Server: is a generic term to designate a server that performs the processing of one or more software applications to client / server architecture.

* Proxy: the server receives requests, and then forwards them to other servers. It can be used to expedite the processing of applications, or enforce regulations (censorship, privacy, etc.).

Example of use on the Internet: Google web application works with more than 15,000 servers in the back-end and these are grouped into clusters of 40 to 80 servers. These are stored in various data processing units all over the world.

Hardware Of A Server

A computer server is used to respond to requests via a network. Miscellaneous assemblers and manufacturers such as HP, Sun and IBM sell computers optimized for this purpose.

These machines are typically high-end designed professionally to serve many clients simultaneously. These machines are equipped with powerful processor or multiple processors. They have lots of memory and fast hard drives of very high capacity, and of course use network interfaces.

The servers are running without intervention, 24 to 24 hours, almost 99.9 percent of the time.

The servers can be mounted in 19 inch rack, which allows stacking them together. They can be equipped with devices to prevent breakdowns and loss of information, such as RAID devices: the information is copied to several hard drives in order to avoid irretrievable loss in case of failure of a hard disk.

The consolidation of multiple servers in a cluster is used to distribute the load, and ensures that customers are served even in case of a server.

A Network Attached Storage is a turnkey appliance, designed specifically as file server. There are also devices for turnkey print servers.

The servers are sometimes connected to storage networks: a set of servers are connected by a fiber optic network to a series of hard drives. The storage battery of the disk is divided into partitions divided between servers.

A device server may run multiple servers simultaneously, and typically serves many users simultaneously. A server is often manipulated, and the keyboard and the screen (if any) used mainly in the maintenance, repair and control.

A server base (in 2008) has a power of 200W with an estimated power consumption of all the computer servers at about 450 TWh in France and 4,000 TWh for the United States.

Continued…

What Is A Server?

In a computer network, a server is a computer and software whose role is to respond automatically to requests sent by clients - computers and software - via the network.

The servers are commonly used in the treatment of data, companies, institutions, and the Internet, or they are often a focal point and are used simultaneously by many users to store, share and exchange information. Different users can operate the server from different clients, for example, from a personal computer, workstation, or terminal.

The World Wide Web, electronic mail and file sharing are some applications that make use of servers.

History Of Server

The first generation of programmable computers emerged in the 1950s. The computer then flew through a terminal or a teletype.

Since the 1970s, computers have sufficient computing power to perform multiple processes simultaneously. Miniaturization and lower prices have allowed the use of personal computer on a mass scale since the 1980s. These personal computers (PCs) could be connected to computers with a terminal emulator software. Users of personal computers mutually exchanged files by copying to floppy disks and floppy disks, which were then removed and inserted on the recipient’s computer.

In 1980 appeared the first file servers. They facilitated the exchange of files between users. Used in institutions, they have successfully allowed multiple users to run the same software simultaneously. A single copy of the software is stored on the file server, and the processing of the software is executed by the clients using the server to sends files to and fro between the users and the server.

A few years later the computing power of personal computers exceeded that of recent computers installed in institutions.

When a computer is connected to a central computer via a terminal emulator, the central computer performs all the treatments, and the computer computes the results. On the contrary, when a file server is used, the server performs no processing - all processing is done by client computers. The idea of using the server to do the processing became a reality (to share the computing and sharing between the mainframe and personal computer) with the arrival of the client-server architecture technology.

In the 1990s came the three-tier architecture, an evolution of client-server architecture, which will separate treatment in 3 parts, processed by a client and two servers.

According to the firm Netcraft, in March 2009, over 220 million web servers in the world were present, and the number is increasing steadily since the invention of the World Wide Web in 1995.

Distributed Application Technique Used In Servers

A distributed application is an application in which salaries are distributed among several computers on a network. A communications protocol establishes the rules by which computers communicate and cooperate.

In an application in client / server processing is done by the joint implementation of two different and complementary software placed on computers: the client and the server.

The client makes requests, and then transmits to the server. The server receives and processes applications, and then sends its reply to the client. The client receives the response (for example, presents the results on screen). A communications protocol establishes the format of requests sent to the server, and responses to it.

The Peer-to-peer (or P2P) is the opposite of the client-server mode.

Continued…

What Is A Laptop?

A laptop or a Laptop PC is a portable personal computer which, thanks to a light weight design and a device that occupies a limited space, can be transported easily which was not possible with a personal desktop computer.

History Of Laptop

One of the first laptops was developed in 1982

The first laptop was created by Adam Osborne in 1981, USA, and its first portable model was called the Osborne I. It weighed about 11 kg and has a 64 KB RAM with subsystem CP/M 8 bits.

Supplied without the hard disk, it was equipped with two floppy drives that were flexible format 5 “1 / 4 with a capacity of less than 80 kb., and had a screen that measured 5″ diagonal (displaying green on black background).

It was designed to place it under the passenger seat on the plane to avoid storing it in the baggage compartment. It came with a set of standard office programs for use in a professional setting. It could be equipped with a 12 volt battery, making it more autonomous.

Its rival was the Kaypro, which was much more rustic in its making and it looked rather like it was meant as a laboratory machine, but it was equipped with a screen size of 9″ in diagonal measurement, had increased drive capacity, and often had a hard disk.

Beginning in 1985 with the arrival of Toshiba Papman, people begin to easily use the portable laptop. It meant that the machine was also equipped with a battery and could be used anywhere. The Papman was the first “true” portable PC.

Carried by the wave of netBook (with standard 10-inch screen), sales of notebooks have for the first time in the 3rd quarter of 2008 exceeded those of desktop computers.

A laptop includes:

* CPU with motherboard, memory, RAM;
* Floppy drive (less delivered from 2000);
* Hard drive for several years (the use of flash memory becomes possible, thus saving energy and a read access faster for small files);
* Flat screen (the first were fitted with CRT small diagonal);
* Keyboard (reduced, without a separate numeric keypad);
* Different standard connectors to complete their equipment externally (network, USB, etc …)
* Tablet (touchpad) replacing the mouse and its buttons.
* More and more often a Wi-Fi Connection and / or Bluetooth

The laptops are more expensive than desktop PCs (due to miniaturization and lack of mass production of components), and are slower (because it must not generate too much heat and avoid consuming too much energy for a better battery life).

To meet these two requirements, they are equipped with a processor “gook” and a small hard disk space (in 2007, it was 2-½”).

Processors of a laptop are specially designed to manage energy consumption. The main problem on a laptop is the low-availability power output of its battery (few hours).

There are other types of laptops:

* Transport: heavier (between 4 and 7 kg), they carry more powerful components such as a hard disk 3 “½, a 3D graphics card and a screen larger
* Ultraportables: much lighter (between 1 and 2 kg), or even smaller, they maintain very good performance but are more expensive
* NetBook: Ultraportables new category of similar size, they are slower (which saves battery), less vulnerable to shocks and sold at a price significantly lower
* Tablet PC (or tablet PC): ultraportable computer equipped with a touchscreen
* Electronic book (or Livrel).

~Thanks to Wikipedia.

What Is A Personal Computer

A personal computer, also known as micro-computer or computer is a computer intended for use by a person and whose dimensions are small enough to fit on a desk.

Functional architecture of the micro-computer

The microcomputer is a system of automatic processing of information, which receives input information (input devices), allows the temporary storage and processing (CPU), backup and archiving (devices storage and backup), communication (peripheral input / output), display and printing (output devices).

History and evolution

Personal computers have emerged when the cost and size of computers have been sufficiently reduced to be sold to the general public. Before that, the computers produced by the machinery industry were central shared among many users who accessed the digital terminals.

The history of personal computers is partly confused with that of microprocessors. The first machines were built kit in the 1970s after creating the first microprocessor, the Intel 4004. The question of who created the first microcomputer is a source of controversy.

* If one considers the first kit, it seems to be an Intel kit MCS4 in 1971.
* If one considers the first machine sold any meeting ready to use, it is the Micral of the French company R2E in 1972.
* Looking at the first personal computer (designed for and sold to individuals), it is the Altair 8800 in 1975.

The first personal computers was very popular and often cited as having introduced all the “revolution” of the personal computer appeared in 1977. These pioneer magnificent computers that began the personal computer  revolution are:

* Apple II Apple;
* The TRS-80 Tandy;
* Commodore PET Commodore International.

In 1981 IBM produced the IBM PC. This personal computer and its offspring, the compatible PC, have gradually dominated the market, approaching 100%. The latest personal computer to occupy a significant place in the market is the Apple Macintosh.

However, the growing convergence between the material used in the Macintosh and the one used in PCs - up to the adoption, in 2006, Intel processors by Apple - minimize the traditional gap between the two worlds. The main differences between micro-computers will now focus on their operating systems.

Some accessories of personal computers are as follows:

1. Monitor
2. Motherboard
3. Processor
4. ATA connectors
5. RAM
6. Expansion card
7. Food
8. CD
9. HDD
10. Keyboard
11. Mouse

Compiling a list of all personal computers that have existed until now is a difficult task. Here is a chronological list of some personal computers that have marked their era:

* Kenbak-1 (1971), sold by mail order without microprocessor.
* Micral (1972-1973), among the big calculator and computer
* Altair 8800 (1975), sold in kit, the first software from Microsoft (BASIC) is designed for it
* IBM 5100 and 5110 (1975-1977), and APL languages BASIC in ROM
* Compucolor (1975), the first to be displayed on a color screen, which was unheard of for a personal computer at the time of its launch
* Apple I, II and III (1976-1980)
* Commodore PET (1977)
* Tandy TRS-80 (1977-1985)
* Sinclair ZX80 and ZX81 (1980, 1981)
* Exidy Sorcerer (1978), the first machine to claim programmable characters
* Texas Instruments TI-99/4A (1979), the first 16 bits of the market
* DAI Imagination Machine (1980), highly oriented music and graphics
* BBC Micro (1981)
* IBM-compatible PC (1981), the source of almost all computers today
* NEC PC-88 and PC-98 (1981)
* Thomson to7 (1982-1984)
* Commodore VIC-20 (1982)
* ZX Spectrum (1982)
* Oric 1 (1982) Oric Atmos (1984)
* Philips VG5000 (1984)
* Sinclair QL (1984)
* Thomson MO5 (1984-1986)
* Apple Lisa (1983), the first personal computer to offer a mouse and a graphical environment.
* Commodore 64 (1983), the personal computer the best-selling
* MSX (1983-1990)
* Amstrad CPC (1984-1989)
* Apple Macintosh (1984), still exists today, but now shares the architecture and IBM-compatible PC
* Amiga (1985)
* Atari ST (1985-1993)
* Acorn Archimedes (1987), the first RISC computer general public
* Sharp X68000 (1987)
* FM Towns (1989)

The global PC market

Market shares of the global PC market in Q3 2007:

* Hewlett Packard (United States) (18.8%)
* Dell (United States) (14.4%)
* Acer (Taiwan) (8.1%)
* Lenovo (former IBM PC division) (China) (8%)
* Toshiba (Japan) (4.4%)
* Other (46.3%)

World market in 2007 according to the audit firm Gartner:

* The number of units sold increased by 13.4% compared to 2006, 271 million units sold worldwide

Market shares by volume in 2007 according to Gartner:

* Hewlett Packard (United States) (19.2%). Growth of 27.4% over one year
* Acer (Taiwan) (13%). Growth of 36.3% over one year
* Dell (United States) (10.5%)
* Lenovo (former IBM PC division) (China)
* Toshiba (Japan). Growth of 26.1% over one year

Buying a computer: Your 2 Choices Are Laptop And Desktop

The price of laptops has declined in recent years and the laptop has become an attractive alternative to the traditional desktop computer.

The laptop has advantages for mobile workers who must carry their computers, such as vendors who visit their clients. However, the desktop is still the most advantageous alternative for sedentary workers and residential users.

Advantages and disadvantages of laptops

Advantages:

* The lightweight and small footprint allow the computer to carry easily.
* The small size is also an advantage for those who have very little space to work or home.
* Facilitate the presentation of products and services or if you have a project to present to jurors (individual or company).
* Confidentiality: the laptop can easily range when not in use.

Disadvantages:

* It is more expensive.
* The replacement of the screen, keyboard and some important components is difficult or impossible.
* Everything is “compressed” (and other components), which promotes failure.
* A laptop is more fragile.
* Suitable hurt heavy multimedia (games , etc.)

Advantages and disadvantages of the desktop

Advantages:

* The ergonomic qualities: The screen and keyboard can be placed at the location and height to maximize comfort.
* The price of a desktop is 20% to 40% less than the price of a laptop power comparable.
* The computer is more robust and better heat evacuates a laptop.
* The computer is also easier and cheaper to repair a laptop.
* After a few years, it is possible to change some parts of a computer to prolong life, which is almost impossible with a laptop.

Disadvantages:

* The major drawback is their size, and thus the difficulty of the move. They require a piece of furniture, even a dedicated room.
~ Acknowledgement and thanks to: Wikipedia.