Overblog Suivre ce blog
Editer l'article Administration Créer mon blog
16 octobre 2010 6 16 /10 /octobre /2010 14:28

This article is about personal computers in general. For computers generally referred to as "PCs", see IBM PC compatible. For hardware components dealing with personal computers, see Personal computer hardware      (Dell XPS M1210 Battery)          .

A personal computer (PC) is any general-purpose computer whose size, capabilities, and original sales price make it useful for individuals, and which is intended to be operated directly by an end user with no intervening computer operator. This is in contrast to the batch processing or time-sharing models which allowed large expensive mainframe systems to be used by many people, usually at the same time, or large data processing systems which required a full-time staff to operate efficiently         (Dell Studio XPS 1340 Battery)          .

It is also in contrast with the more recent trend of controlling software availability through an intervening third party such as the Apple App Store.

A personal computer may be a desktop computer, a laptop, a tablet PC, or a handheld PC (also called a palmtop). The most common microprocessors in personal computers are x86-compatible CPUs        (Dell Studio XPS 1640 Battery)       .

Software applications for personal computers include word processing, spreadsheets, databases, Web browsers and e-mail clients, games, and myriad personal productivity and special-purpose software applications. Modern personal computers often have connections to the Internet, allowing access to the World Wide Web and a wide range of other resources      (Dell Vostro 1710 Battery)        .

A PC may be used at home or in an office. Personal computers may be connected to a local area network (LAN), either by a cable or a wireless connection.

While early PC owners usually had to write their own programs to do anything useful with the machines, today's users have access to a wide range of commercial and non-commercial software, which is provided in ready-to-run or ready-to-compile form. Since the 1980s, Microsoft and Intel have dominated much of the personal computer market, first with MS-DOS and then with the Wintel platform       (ASUS EEE PC900 battery) .

History

This section needs additional citations for verification.

Please help improve this article by adding reliable references. Unsourced material may be challenged and removed. (September 2008)

Main article: History of personal computers   (Dell RM791 battery)

In what was later to be called The Mother of All Demos, SRI researcher Douglas Englebart in 1968 gave a preview of what would become the staples of daily working life in the 21st century - e-mail, hypertext, word processing, video conferencing, and the mouse. The demonstration required technical support staff and a mainframe time-sharing computer that were far too costly for individual business use at the time        (Sony VGP-BPS13 battery)      .

By the early 1970s, people in academic or research institutions had the opportunity for single-person use of a computer system in interactive mode for extended durations, although these systems would still have been too expensive to be owned by a single person.

HP 9830 was an early desktop computer with printer      (sony vgp-bpl9 battery)

In the 1970s Hewlett Packard introduced fully BASIC programmable computers that fit entirely on top of a desk, including a keyboard, a small one-line display and printer. The Wang 2200 of 1973 had a full-size CRT and cassette tape storage. The IBM 5100 in 1975 had a small CRT display and could be programmed in BASIC and APL. These were generally expensive specialized computers sold for business or scientific uses         (Sony VGP-BPL11 battery)     .

The introduction of the microprocessor, a single chip with all the circuitry that formerly occupied large cabinets, led to the proliferation of personal computers after 1975.

Early personal computers - generally called microcomputers - were sold often in kit form and in limited volumes, and were of interest mostly to hobbyists and technicians        (Sony VGP-BPL15 battery)         .

Minimal programming was done with toggle switches to enter instructions, and output was provided by front panel lamps. Practical use required peripherals such as keyboards, computer terminals, disk drives, and printers. Micral N was the earliest commercial, non-kit microcomputer based on a microprocessor, the Intel 8008          (Dell Inspiron E1505 battery )        .

It was built starting in 1972 and about 90,000 units were sold. The first true Personal Computer was the Sphere 1 computer, created in Bountiful, Utah in 1975 by computer pioneer Michael D. Wise (1949-2002). At first, Sphere 1 was sold as a kit, but was later sold as fully assembled PC. The Sphere 1 qualified as The First Personal Computer because it included a keyboard, a number pad, and a monitor         (Dell Latitude E6400 battery)         .

In 1976 Steve Jobs and Steve Wozniak sold the Apple I computer circuit board, which was fully prepared and contained about 30 chips. The first successfully mass marketed personal computer was the Commodore PET introduced in January 1977, which bore a striking resemblance to Sphere 1 of two years earlier. It was soon followed by the TRS-80 from Radio Shack and the popular Apple II. Mass-market pre-assembled computers allowed a wider range of people to use computers, focusing more on software applications and less on development of the processor hardware       (HP Pavilion dv6000 Battery)        .

Through the late 1970s and into the 1980s, computers were developed for household use, with software for personal productivity, programming and games. One such machine, the Commodore 64, totaled 17 million units sold, making it the best-selling single personal computer model of all time       (Hp Pavilion dv3-1000 battery)       .

Somewhat larger and more expensive systems (although still low-cost compared with minicomputers and mainframes) were aimed at office and small business use. Workstations are characterized by high-performance processors and graphics displays, with large local disk storage, networking capability, and running under a multitasking operating system        (Dell Precision M70 Battery)        .

In 1984, Dr. Mark Dean created a device called the ISA systems bus, which allows a personal computer to have several machines connected to it at once, such as a printer and scanner or modem. ISA is widely used today and Dean also received the Black Engineer of the Year President’s Award in 1997 for his contribution . However, card slots already existed before the ISA bus of the IBM-PC in the Apple         (Acer Aspire One battery)         .

IBM 5150 as of 1981

Eventually due to the influence of the IBM-PC on the personal computer market, personal computers and home computers lost any technical distinction. Business computers acquired color graphics capability and sound, and home computers and game systems users used the same processors and operating systems as office workers. Mass-market computers had graphics capabilities and memory comparable to dedicated workstations of a few years before        (Toshiba Satellite L305 Battery)        .

Even local area networking, originally a way to allow business computers to share expensive mass storage and peripherals, became a standard feature of personal computers used at home.

Market and sales

See also: Market share of leading PC vendors

Personal computers worldwide in million distinguished by developed and developing world    (Toshiba Satellite Pro M15 Battery)

In 2001, 125 million personal computers were shipped in comparison to 48 thousand in 1977. More than 500 million personal computers were in use in 2002 and one billion personal computers had been sold worldwide from the mid-1970s up to this time. Of the latter figure, 75 percent were professional or work related, while the rest were sold for personal or home use. About 81.5 percent of personal computers shipped had been desktop computers, 16.4 percent laptops and 2.1 percent servers       (Toshiba Satellite M65 battery)          .

The United States had received 38.8 percent (394 million) of the computers shipped, Europe 25 percent and 11.7 percent had gone to the Asia-Pacific region, the fastest-growing market as of 2002. The second billion was expected to be sold by 2008. Almost half of all the households in Western Europe had a personal computer and a computer could be found in 40 percent of homes in United Kingdom, compared with only 13 percent in 1985         (Toshiba Satellite T4900 Battery)        .

The global personal computer shipments were 264 million units in the year 2007, according to iSuppli,  up 11.2 percent from 239 million in 2006.  In 2004, the global shipments were 183 million units, an 11.6 percent increase over 2003. In 2003, 152.6 million computers were shipped, at an estimated value of $175 billion. In 2002, 136.7 million PCs were shipped, at an estimated value of $175 billion     (Toshiba PA3399U-2BRS battery)        .

In 2000, 140.2 million personal computers were shipped, at an estimated value of $226 billion.  Worldwide shipments of personal computers surpassed the 100-million mark in 1999, growing to 113.5 million units from 93.3 million units in 1998.  In 1999, Asia had 14.1 million units shipped        (Toshiba Satellite A200 Battery)       .

As of June 2008, the number of personal computers in use worldwide hit one billion, while another billion is expected to be reached by 2014. Mature markets like the United States, Western Europe and Japan accounted for 58 percent of the worldwide installed PCs. The emerging markets were expected to double their installed PCs by 2012 and to take 70 percent of the second billion PCs. About 180 million computers (16 percent of the existing installed base) were expected to be replaced and 35 million to be dumped into landfill in 2008. The whole installed base grew 12 percent annually      (Toshiba Satellite 1200 Battery)       .

In the developed world, there has been a vendor tradition to keep adding functions to maintain high prices of personal computers. However, since the introduction of the One Laptop per Child foundation and its low-cost XO-1 laptop, the computing industry started to pursue the price too. Although introduced only one year earlier, there were 14 million netbooks sold in 2008     (Toshiba NB100 Battery).

Besides the regular computer manufacturers, companies making especially rugged versions of computers have sprung up, offering alternatives for people operating their machines in extreme weather or environments.

Average selling price

For Microsoft Windows systems, the average selling price (ASP) showed a decline in 2008/2009, possibly due to low-cost netbooks, drawing $569 for desktop computers and $689 for laptops at U.S. retail in August 2008. In 2009, ASP had further fallen to $533 for desktops and to $602 for notebooks by January and to $540 and $560 in February       (Toshiba Satellite M300 Battery)         .

According to research firm NPD, the average selling price of all Windows portable PCs has fallen from $659 in October 2008 to $519 in October 2009.

Types

Workstation

Sun SPARCstation 1+, 25 MHz RISC processor from early 1990s

Main article: Workstation       (Dell INSPIRON 1525 battery)

A workstation is a high-end personal computer designed for technical or scientific applications. Intended primarily to be used by one person at a time, they are commonly connected to a local area network and run multi-user operating systems. Workstations are used for tasks such as computer-aided design, drafting and modelling, computation-intensive scientific and engineering calculations, image processing, architectural modelling, and computer graphics for animation and motion picture visual effects      (SONY VAIO VGN-FZ280E Battery)        .

Desktop computer

Main article: Desktop computer

Dell OptiPlex desktop computer

Prior to the wide spread of PCs a computer that could fit on a desk was considered remarkably small. Today the phrase usually indicates a particular style of computer case          (SONY VAIO VGN-FZ410 Battery)      .

Desktop computers come in a variety of styles ranging from large vertical tower cases to small form factor models that can be tucked behind an LCD monitor. In this sense, the term 'desktop' refers specifically to a horizontally-oriented case, usually intended to have the display screen placed on top to save space on the desk top. Most modern desktop computers have separate screens and keyboards       (SONY VAIO VGN-FZ160 Battery)         .

Single unit

Single unit PCs (also known as all-in-one PCs) are a subtype of desktop computers, which combine the monitor and case of the computer within a single unit. The monitor often utilizes a touchscreen as an optional method of user input, however detached keyboards and mice are normally still included. The inner components of the PC are often located directly behind the monitor, and many are built similarly to laptops       (SONY VAIO VGN-FZ38M Battery)       .

Nettop

Main article: Nettop

A subtype of desktops, called nettops, was introduced by Intel in February 2008 to describe low-cost, lean-function, desktop computers. A similar subtype of laptops (or notebooks) are the netbooks (see below). These feature the new Intel Atom processor which specially enables them to consume less power and to be built into small enclosures         (SONY VAIO VGN-FZ21m Battery)  .

Laptop

Main article: Laptop

Acer 8920 Gemstone Laptop.

A laptop computer or simply laptop, also called a notebook computer or sometimes a notebook, is a small personal computer designed for portability. Usually all of the interface hardware needed to operate the laptop, such as USB ports (previously parallel and serial ports), graphics card, sound channel, etc., are built in to a single unit        (SONY VAIO VGN-FZ18m Battery)      .

Laptops contain high capacity batteries that can power the device for extensive periods of time, enhancing portability. Once the battery charge is depleted, it will have to be recharged through a power outlet. In the interest of saving power, weight and space, they usually share RAM with the video channel, slowing their performance compared to an equivalent desktop machine     (SONY VAIO VGN-FZ11m Battery)         .

One main drawback of the laptop is sometimes, due to the size and configuration of components, relatively little can be done to upgrade the overall computer from its original design. Internal upgrades are either not manufacturer recommended, can damage the laptop if done with poor care or knowledge, or in some cases impossible, making the desktop PC more modular. Some internal upgrades, such as memory and hard disks upgrades are often easy, a display or keyboard upgrade is usually impossible        (SONY VAIO VGN-FZ11z Battery)          .

The laptop has the same access as the desktop to the wide variety of devices, such as external displays, mice, cameras, storage devices and keyboards, which may be attached externally through USB ports and other less common ports such as external video.

A subtype of notebooks, called subnotebooks, are computers with most of the features of a standard laptop computer but smaller          (SONY VAIO VGN-FZ11l Battery)      .

They are larger than hand-held computers, and usually run full versions of desktop/laptop operating systems. Ultra-Mobile PCs (UMPC) are usually considered subnotebooks, or more specifically, subnotebook Tablet PCs (see below). Netbooks are sometimes considered in this category, though they are sometimes separated in a category of their own (see below).

Desktop replacements, meanwhile, are large laptops meant to replace a desktop computer while keeping the mobility of a laptop. Entertainment laptops emphasize large, HDTV-resolution screens and video processing capabilities     (SONY VAIO VGN-FZ31z Battery)        .

Netbook

Main article: Netbook

An HP netbook

Netbooks (also called mini notebooks or subnotebooks) are a rapidly evolving category of small, light and inexpensive laptop computers suited for general computing and accessing web-based applications; they are often marketed as "companion devices," that is, to augment a user's other computer access    (Dell Studio 1555 Battery)       .

Walt Mossberg called them a "relatively new category of small, light, minimalist and cheap laptops."  By August 2009, CNET called netbooks "nothing more than smaller, cheaper notebooks."

At their inception in late 2007 — as smaller notebooks optimized for low weight and low cost— netbooks omitted key features (e.g., the optical drive), featured smaller screens and keyboards, and offered reduced specification and computing power    (Dell Vostro 1720 Battery)        .

Over the course of their evolution, netbooks have ranged in size from below 5 in to over 13 in, and from ~1 kg (2-3 pounds). Often significantly less expensive than other laptops,by mid-2009, netbooks had been offered to users "free of charge", with an extended service contract purchase of a cellular data plan      (Dell Vostro 1500 Battery)       .

In the short period since their appearance, netbooks have grown in size and features, now converging with new smaller, lighter notebooks. By mid 2009, CNET noted "the specs are so similar that the average shopper would likely be confused as to why one is better than the other," noting "the only conclusion is that there really is no distinction between the devices      (Dell Latitude D830 Battery)        ."

Tablet PC

Main article: Tablet PC

HP Compaq tablet PC with rotating/removable keyboard.

A tablet PC is a notebook or slate-shaped mobile computer, first introduced by Pen computing in the early 90s with their PenGo Tablet Computer and popularized by Microsoft      (Dell Latitude D620 Battery)      .

Its touchscreen or graphics tablet/screen hybrid technology allows the user to operate the computer with a stylus or digital pen, or a fingertip, instead of a keyboard or mouse. The form factor offers a more mobile way to interact with a computer. Tablet PCs are often used where normal notebooks are impractical or unwieldy, or do not provide the needed functionality         (SONY VAIO VGN-FZ150E Battery)         .

As technology and functionality continue to progress, prototype tablet PCs will continue to emerge. The Microsoft Courier, a personal business device, has two 7" monitors that support multi-touch gestures, Wi-Fi capabilities and has a built-in camera. The device looks to be a replacement to traditional planners while offering what most digital planners cannot, two pages and large writing spaces. This particular device, however, has been recently abandoned and the market is currently being led by the popular iPad from Apple Inc         (Dell Studio 1735 Battery)       .

Ultra-Mobile PC

Main article: Ultra-Mobile PC

Samsung Q1 Ultra-Mobile PC.

The ultra-mobile PC (UMPC) is a specification for a small form factor of tablet PCs. It was developed as a joint development exercise by Microsoft, Intel, and Samsung, among others. Current UMPCs typically feature the Windows XP, Windows Vista, Windows 7, or Linux operating system and low-voltage Intel Atom or VIA C7-M processors        (Dell Inspiron 300M Battery)    .

Home theater PC

Main article: Home theater PC

Antec Fusion V2 home theater PC with keyboard on top.

A home theater PC (HTPC) is a convergence device that combines the functions of a personal computer and a digital video recorder. It is connected to a television or a television-sized computer display and is often used as a digital photo, music, video player, TV receiver and digital video recorder      (Dell Studio 1737 battery)       .

Home theater PCs are also referred to as media center systems or media servers. The general goal in a HTPC is usually to combine many or all components of a home theater setup into one box. They can be purchased pre-configured with the required hardware and software needed to add television programming to the PC, or can be cobbled together out of discrete components as is commonly done with MythTV, Windows Media Center, GB-PVR, SageTV, Famulent or LinuxMCE      (Dell XPS M1530 battery)      .

Pocket PC

Main article: Pocket PC

An O2 pocket PC

A pocket PC is a hardware specification for a handheld-sized computer (personal digital assistant) that runs the Microsoft Windows Mobile operating system. It may have the capability to run an alternative operating system like NetBSD or Linux. It has many of the capabilities of modern desktop PCs       (Dell XPS M2010 battery)          .

Currently there are tens of thousands of applications for handhelds adhering to the Microsoft Pocket PC specification, many of which are freeware. Some of these devices also include mobile phone features. Microsoft compliant Pocket PCs can also be used with many other add-ons like GPS receivers, barcode readers, RFID readers, and cameras. In 2007, with the release of Windows Mobile 6, Microsoft dropped the name Pocket PC in favor of a new naming scheme       (Dell Vostro 1000 battery)       .

Devices without an integrated phone are called Windows Mobile Classic instead of Pocket PC. Devices with an integrated phone and a touch screen are called Windows Mobile Professional.

Motherboard

The motherboard, also referred to as systemboard or mainboard, is the primary circuit board within a personal computer. Many other components connect directly or indirectly to the motherboard        (HP Pavilion dv9000 battery)         .

Motherboards usually contain one or more CPUs, supporting circuitry - usually integrated circuits (ICs) - providing the interface between the CPU memory and input/output peripheral circuits, main memory, and facilities for initial setup of the computer immediately after power-on (often called boot firmware or, in IBM PC compatible computers, a BIOS). In many portable and embedded personal computers, the motherboard houses nearly all of the PC's core components       (Hp 520 battery)       .

Often a motherboard will also contain one or more peripheral buses and physical connectors for expansion purposes. Sometimes a secondary daughter board is connected to the motherboard to provide further expandability or to satisfy space constraints.

Main memory

Main article: Primary storage

A PC's main memory is fast storage that is directly accessible by the CPU, and is used to store the currently executing program and immediately needed data. PCs use semiconductor random access memory (RAM) of various kinds such as DRAM, SDRAM or SRAM as their primary storage       (SONY VGP-BPS13 Battery)      .

Which exact kind depends on cost/performance issues at any particular time. Main memory is much faster than mass storage devices like hard disks or optical discs, but is usually volatile, meaning it does not retain its contents (instructions or data) in the absence of power, and is much more expensive for a given capacity than is most mass storage. Main memory is generally not suitable for long-term or archival data storage     (SONY VAIO VGN-FZ Battery)   .

Hard disk

Main article: Hard disk drive

A Western Digital 250 GB hard disk drive.

Mass storage devices store programs and data even when the power is off; they do require power to perform read and write functions during usage. Although flash memory has dropped in cost, the prevailing form of mass storage in personal computers is still the hard disk       (Dell RM791 battery)        .

The disk drives use a sealed head/disk assembly (HDA) which was first introduced by IBM's "Winchester" disk system. The use of a sealed assembly allowed the use of positive air pressure to drive out particles from the surface of the disk, which improves reliability.

If the mass storage controller provides for expandability, a PC may also be upgraded by the addition of extra hard disk or optical disc drives. For example, BD-ROMs, DVD-RWs, and various optical disc recorders may all be added by the user to certain PCs     (Toshiba Portege R200 Battery) .

Standard internal storage device connection interfaces are PATA, Serial ATA, SCSI

Video card

Main article: Video card

ATI Radeon video card

The video card - otherwise called a graphics card, graphics adapter or video adapter - processes and renders the graphics output from the computer to the computer display, and is an essential part of the modern computer. On older models, and today on budget models, graphics circuitry tended to be integrated with the motherboard but, for modern flexible machines, they are supplied in PCI, AGP, or PCI Express format        (Toshiba Satellite M60 battery)          .

When the IBM PC was introduced, most existing business-oriented personal computers used text-only display adapters and had no graphics capability. Home computers at that time had graphics compatible with television signals, but with low resolution by modern standards owing to the limited memory available to the eight-bit processors available at the time      (Dell Studio 1555 Battery)      .

Visual display unit

Main article: Visual display unit

A flat-panel LCD monitor.

A visual display unit (or monitor) is a piece of electrical equipment, usually separate from the computer case, which displays viewable images generated by a computer without producing a permanent record      (Dell Vostro 1400 Battery)         .

The word "monitor" is used in other contexts; in particular in television broadcasting, where a television picture is displayed to a high standard. A computer display device is usually either a cathode ray tube or some form of flat panel such as a TFT LCD. The monitor comprises the display device, circuitry to generate a picture from electronic signals sent by the computer, and an enclosure or case  (Dell Vostro 1500 Battery)      .

Within the computer, either as an integral part or a plugged-in Expansion card, there is circuitry to convert internal data to a format compatible with a monitor. The images from monitors originally contained only text, but as Graphical user interfaces emerged and became common, they began to display more images and multimedia content     (Toshiba Satellite Pro M50 Battery)     .

Keyboard

Main article: Keyboard (computing)

A computer keyboard

In computing, a keyboard is an arrangement of buttons that each correspond to a function, letter, or number. They are the primary devices of inputing text. In most cases, they contain an array of keys specifically organized with the corresponding letters, numbers, and functions printed or engraved on the button      (Dell Vostro 1510 Battery)        .

They are generally designed around an operators language, and many different versions for different languages exist. In English, the most common layout is the QWERTY layout, which was originally used in typewriters. They have evolved over time, and have been modified for use in computers with the addition of function keys, number keys, arrow keys, and OS specific keys       (Dell Latitude XT2 Tablet PC Battery)       .

Often, specific functions can be achieved by pressing multiple keys at once or in succession, such as inputing characters with accents or opening a task manager. Programs use keyboard shotcuts very differently and all use different keyboard shortcuts for different program specific operations, such as refreshing a web page in a web browser or selecting all text in a word processor     (Dell Vostro A90 Battery)          .

Mouse

Main article: Mouse (computing)

Apple Mighty Mouse that detects the right and left clicks through what appears to be one large button.

A Mouse on a computer is a small, slidable device that users hold and slide around to point at, click on, and sometimes drag objects on screen in a graphical user interface using a pointer on screen. Almost all Personal Computers have mice        ( HP Pavilion DV7 Battery)         .

It may be plugged into a computer's rear mouse socket, or as a USB device, or, more recently, may be connected wirelessly via a USB antenna or Bluetooth antenna. In the past, they had a single button that users could press down on the device to "click" on whatever the pointer on the screen was hovering over          ( HP Pavilion DV7 Battery)      .

Now, however, many Mice have two or three buttons(possibly more); a "right click" function button on the mouse, which performs a secondary action on a selected object, and a scroll wheel, which users can rotate using their fingers to "scroll" up or down. The scroll wheel can also be pressed down, and therefore be used as a third button. Some mouse wheels may be tilted from side to side to allow sideways scrolling. Different programs make use of these functions differently, and may scroll horizontally by default with the scroll wheel, open different menus with different buttons, among others. These functions may be user defined through software utilities   (Toshiba Satellite Pro M10 Battery)        .

Mice traditionally detected movement and communicated with the computer with an internal "mouse ball"; and used optical encoders to detect rotation of the ball and tell the computer where the mouse has moved. However, these systems were subject to low durability, accuracy and required internal cleaning. Modern mice use optical technology to directly trace movement of the surface under the mouse and are much more accurate, durable and almost maintenace free. They work on a wider variety of surfaces and can even operate on walls, ceilings or other non-horizontal surfaces      (Dell Inspiron 300M Battery)      .

Partager cet article

Repost 0
Published by batterys
commenter cet article

commentaires