Personal computer
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http://en.wikipedia.org/wiki/Personal_computer
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| A stylized illustration of a desktop
computer |
A personal computer (PC) is any computer
whose original sales price, size, and capabilities make
it useful for individuals, and which is intended to be operated
directly by an end user, with no intervening computer operator.
Today a PC may
be a desktop computer, a laptop computer or a tablet computer. The most common operating systems are Microsoft Windows, Mac
OS and Linux,
while the most common microprocessors are x86-compatible
CPUs. Software applications for personal computers include word processing, spreadsheets, databases, games, and
a myriad of personal productivity and special-purpose software. Modern personal
computers often have high-speed or dial-up connections to the Internet,
allowing access to the World Wide Web and a wide range of other
resources.
A PC may be a home computer, or may be found in an office,
often connected to a local area network. The
distinguishing characteristics are that the computer is primarily used,
interactively, by one person at a time. This is in contrast to the batch
processing or time-sharing models which allowed large expensive 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.
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 easily installed.
Contents
History
 |
| IBM
5150 as of 1981 |
The capabilities
of the PC have changed greatly since the introduction of electronic computers.
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. 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 about 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. By the late 1970s, 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.
Throughout the
1970s and 1980s, home computers were developed for household
use, offering personal productivity, programming and games. Somewhat larger and
more expensive systems (although still low-cost compared with minicomputers and mainframes)
were aimed for 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. Workstations are still 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.
Eventually the
market segments 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. Even local area networking, originally a
way to allow business computers to share expensive mass storage and
peripherals, became a standard feature of the personal computers used at home.
Market
In 2001 125 million personal computers were shipped in comparison to 48 thousand in 1977.
More than 500 million PCs were in use in 2002 and
one billion personal computers had been sold worldwide since mid-1970s till this time. Of
the latter figure, 75 percent were professional or work related, while the rest
sold for personal or home use. About 81.5 percent of PCs shipped had been desktop computers, 16.4 percent laptops and
2.1 percent servers. United States had received 38.8 percent (394
million) of the computers shipped, Europe 25
percent and 11.7 percent had gone to Asia-Pacific region, the fastest-growing
market as of 2002. The
second billion was expected to be sold by 2008.[2] 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.[3]
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 2013 and
to take 70 percent of the second billion PCs. About 180 million PCs (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.[4][5]
Rugged computer industry
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. [6]
Netbooks and nettops
The emergence of
new market segment of small, energy-efficient and low-cost devices (netbooks and nettops)
could threaten established companies like Microsoft, Intel, HP or Dell,
analysts said in July 2008. A market research firm International Data
Corporation predicted that the category could grow
from fewer than 500,000 in 2007 to 9 million in 2012 as
the market for low cost and secondhand computers expands in
developed economies. [7] Also, after Microsoft ceased selling of Windows XP for ordinary machines, it made an
exception and continued to offer the operating system for netbook and nettop makers.[8]
Types
Desktop Computer
 |
| Dell OptiPlex desktop computer |
A desktop
computer is an independent personal computer (PC), as opposed to smaller forms
of PCs, such as a mobile laptop.
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. 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.
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).
Laptop
A laptop
computer or simply laptop,
also called a notebook computer or sometimes a notebook, is a small personal
computer designed for mobility. Usually all of the interface hardware needed to
operate the laptop, such as parallel and serial ports, graphics card, sound channel,
etc., are built in to a single unit. Most laptops contain batteries to
facilitate operation without a readily available electrical 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.
 |
| A
modern mid-range HP Laptop |
One main
drawback of the laptop is that, due to the size and configuration of
components, relatively little can be done to upgrade the overall computer from
its original design. Some devices can be attached externally through ports
(including via USB), however internal upgrades are not recommended or in some
cases impossible, making the desktop PC more modular.
A subtype of
notebooks, called subnotebooks, are computers with most of the
features of a standard laptop computer but smaller. 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.
Netbook
 |
| Black ASUS Eee PC in proportions comparison with tissues |
Netbook PCs
are small portable computers in a "clamshell"
design, that are designed specifically for wireless communication and access to
the Internet. They are generally much lighter and cheaper than subnotebooks, and have a smaller display,
between 7" and 9", with a screen resolution between 800x600 and
1024x768. The operating systems and applications on them are usually specially
modified so they can be comfortably used with a smaller sized screen, and the OS is often based on Linux,
although some Netbooks also use Windows XP. Some Netbooks make use of their
built in high speed Wireless connectivity to offload some of their applications
software to Internet servers, through the principle of Cloud computing, as most Netbooks have small solid state storage systems instead of hard-disks. Storage capacities are usually in the 4 to 12 GB
range. One of the first examples of such a system was the original EEE
PC.
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. 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.
Ultra-Mobile PC
 |
| Samsung Q1 Ultra-Mobile PC |
The ultra-mobile
PC (UMPC) is a specification for a small form factor tablet PC. It was developed as a joint
development exercise by Microsoft, Intel, and Samsung,
among others. Current UMPCs typically feature the Windows XP Tablet PC
Edition 2005, Windows Vista Home Premium Edition, or Linux operating system and low-voltage Intel Pentium or VIA
C7-M processors in the 1 GHz range.
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. 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 Windows Media Center, GB-PVR, SageTV,
Famulent or LinuxMCE.
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.
Currently there
are 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. 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.[9]
Hardware
 |
An
exploded view of a modern personal computer and peripherals:
- Scanner
- CPU (Microprocessor)
- Primary
storage (RAM)
- Expansion cards (graphics cards, etc)
- Power
supply
- Optical
disc drive
- Secondary storage (Hard disk)
- Motherboard
- Speakers
- Monitor
- System
software
- Application software
- Keyboard
- Mouse
- External hard disk
- Printer
|
A typical
hardware setup of a desktop computer consists of:
- computer
case with power supply
- central processing unit (processor)
- motherboard
- memory
card
- hard
disk
- video
card
- visual display unit (monitor)
- optical disc (usually DVD-ROM or DVD Writer)
- keyboard and pointing
device
These components
can usually be put together with little knowledge to build a computer. The
motherboard is a main part of a computer that connects all devices together.
The memory card(s), graphics card and processor are mounted directly onto the
motherboard (the processor in a socket and the memory and graphics cards in expansion slots). The mass storage is connected
to it with cables and can be installed in the computer case or in a separate
case. This is the same for the keyboard and mouse, except that they are
external and connect to the I/O panel on the back of the computer. The monitor
is also connected to the I/O panel, either through an onboard port on the
motherboard, or a port on the graphics card.
Several
functions (implemented by chipsets) can be
integrated into the motherboard, typically USB and
network, but also graphics and sound. Even if these are present, a separate
card can be added if what is available isn't sufficient. The graphics and sound
card can have a break out box to keep the analog parts away
from the electromagnetic radiation inside the computer case. For really large amounts of data, a tape drive can be used or (extra) hard disks can
be put together in an external case.
The hardware capabilities of personal computers can
sometimes be extended by the addition of expansion cards connected via an expansion bus. Some standard peripheral buses often
used for adding expansion cards in personal computers as of 2005 are PCI, AGP (a
high-speed PCI bus dedicated to graphics adapters), and PCI Express. Most personal computers as of 2005
have multiple physical PCI expansion slots. Many also include an AGP bus and expansion slot or a PCI
Express bus and one or more expansion slots, but few PCs contain both buses.
Computer case
 |
| A
stripped ATX case
lying on its side |
A computer case
is the enclosure that contains the main components of a computer.
Cases are usually constructed from steel, aluminium, or plastic,
although other materials such as wood, plexiglas or fans[10] have also been used in case designs.
Cases can come in many different sizes, or form factors. The
size and shape of a computer case is usually determined by the form factor of
the motherboard that it is designed to accommodate,
since this is the largest and most central component of most computers.
Consequently, personal computer form factors typically specify only the internal dimensions and layout of the case. Form factors for rack-mounted and blade servers may
include precise external dimensions as well, since these cases must
themselves fit in specific enclosures.
Currently, the
most popular form factor for desktop computers is ATX,
although microATX and small form factors have become
very popular for a variety of uses. Companies like Shuttle Inc. and AOpen have popularized small cases, for which FlexATX is
the most common motherboard size. Apple Computer has also produced the Mac
Mini computer, which is similar in size to a standard
CD-ROM drive.
Central processing unit
 |
| AMD Athlon 64 CPU |
The central
processing unit, or CPU, is that part of a computer which executes software program instructions. In older computers this
circuitry was formerly on several printed circuit boards, but
in PCs is a single integrated circuit. Nearly all PCs contain a type of CPU
known as a microprocessor. The microprocessor often plugs
into the motherboard using one of many different types of sockets. IBM PC compatible computers use
an x86-compatible
processor, usually made by Intel, AMD, VIA Technologies or Transmeta.
Apple Macintosh computers were initially built with the Motorola 680x0 family of processors, then switched to the PowerPC series (a RISC architecture jointly developed by Apple Computer, IBM and Motorola),
but as of 2006, Apple has switched again, this time to x86 compatible
processors. Modern CPUs are equipped with a fan attached via heat sink.
Motherboard
 |
| Asus 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.
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. 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
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
 |
| 1GB DDR SDRAM 400 module |
immediately needed data. PCs use semiconductor random access memory (RAM) of various kinds such as DRAM or SRAM as
their primary storage. 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.
Hard disk
 |
| 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 semiconductor flash memory has dropped in cost, the prevailing
form of mass storage in personal computers is still the electromechanical hard disk.
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, DVD-ROMs, CD-ROMs, and
various optical disc recorders may all be added by the user to certain PCs.
Standard internal storage device interfaces are ATA, Serial ATA, SCSI, and
CF+ type II in 2005.
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, also called the visual display
unit (VDU), 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.
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.
Visual display unit
 |
| An LG flat-panel LCD monitor |
A visual display
unit (also called 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. 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. Within the computer, either as an integral part or a plugged-in interface,
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.
Keyboards
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 aray of keys specifically organized with the corresponding letters,
numbers, and functions printed or engraved on the button. 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. Often, specific functions can be
aechieved by pressing multiple keys at once or in succession, such as inputing
characters with accents or opening a task manager. Programs use keybord
shotcuts very differently and all use different keyboard shortcuts for
different program specific operations, such as refreshig a web
page in a web browser or selecting all text in a word
processor.
Pointing devices
 |
| Apple Mighty Mouse that
detects the location of your finger, when clicking, with Capacitive sensors. |
A Mouse on a
computer is a small, slidable device that users hold and slide around to point
at, click, and sometimes drag objects on screen in a graphical user interface
using a pointer on screen. Almost all Personal Computers have mice. 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. Now, however, many Mice have two or three buttons; 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 the wheel using their fingers to "scroll" up or down. The
scroll wheel can also be pressed down, and therefore be used as a third button.
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.
Mice
traditionally detected movement and communicated with the computer with an
internal "mouse ball"; and use 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 and accuracy. Modern mice use optical
technology to directly trace movement of the surface under the mouse and are
much more accurate and durable. They work on a wider variety of surfaces and
can even operate on walls, ceilings or other non-horizontal surfaces.
Other components
Mass
storage
All computers
require either fixed or removable storage for their operating system, programs
and user generated material.
Formerly the 5 1/4 inch and 3 1/2 inch floppy drive were the principal forms of
removable storage for backup of user files and distribution of software.
As memory sizes
increased, the capacity of the floppy did not keep pace; the Zip drive and other higher-capacity removable
media were introduced but never became as prevalent as the floppy drive.
By the late
1990s the optical drive, in CD and
later DVD and Blu-ray Disc, became the main method for
software distribution, and writeable media provided backup and file
interchange. Floppy drives have become uncommon in desktop personal computers
since about 2000, and were dropped from many laptop systems even earlier. [11]
Early home computers used compact audio cassettes for file
storage; these were at the time a very low cost storage solution, but were
displaced by floppy disk drives when manfacturing costs dropped, by the mid
1980's.
A second generation
of tape recorders was provided when Videocassette recorders were
pressed into service as backup media for larger disk drives. All these systems
were less reliable and slower than purpose-built magnetic tape drives. Such
tape drives were uncommon in consumer-type personal computers but were a
necessity in business or industrial use.
Interchange of
data such as photographs from digital cameras is greatly expedited by
installation of a card reader, which often is compatible with several
forms of flash memory. It is usually faster and more
convenient to move large amounts of data by removing the card from the mobile
device, instead of communicating with the mobile device through a USB interface.
A USB flash drive today performs much of the data
transfer and backup functions formerly done with floppy drives, Zip disks and
other devices. Main-stream current operating systems for personal computers
provide standard support for flash drives, allowing interchange even between
computers using different processors and operating systems. The compact size
and lack of moving parts or dirt-sensitive media, combined with low cost for high
capacity, have made flash drives a popular and useful accessory for any
personal computer user.
The operating system (e.g.: Microsoft Windows, Mac
OS, Linux or
many others) can be located on any removable storage, but typically it is on
one of the hard disks. A Live
CD is also possible, but it is very slow and is usually used for installation of
the OS, demonstrations, or problem solving. Flash-based memory is currently
expensive (as of mid-2008) but is starting to appear in laptop computers
because of its low weight and low energy consumption, compared to hard disk
storage.
Computer
communications
- Internal
modem card
- Modem
- Network
adapter card
- Router
Common peripherals and adapter cards
- Headset
- Joystick
- Microphone
- Printer
- Scanner
- Sound adapter card as a
separate card rather than located on the motherboard
- Speakers
- Webcam
Software
 |
| A screenshot of the OpenOffice.org Writer software |
Computer
software is a general term used to describe a collection of computer programs, procedures and documentation that perform some
tasks on a computer system.[12] The term includes application software such
as word processors which perform productive tasks
for users, system software such as operating systems, which
interface with hardware to
provide the necessary services for application software, and middleware which controls and co-ordinates distributed systems.
Software
applications for word processing, Internet browsing, Internet faxing, e-mail and
other digital messaging, multimedia playback, computer game play and computer programming are
common. The user of a modern personal computer may have significant knowledge
of the operating environment and application programs, but is not necessarily
interested in programming nor even able to write programs for the computer.
Therefore, most software written primarily for personal computers tends to be designed with simplicity
of use, or "user-friendliness"
in mind. However, the software industry continuously
provide a wide range of new products for use in personal computers, targeted at
both the expert and the non-expert user.
Operating system
 |
| KDE 4 running on a Linux distribution |
An operating
system (OS) manages computer resources and provides programmers with an interface used
to access those resources. An operating system processes system data and user
input, and responds by allocating and managing tasks and internal system
resources as a service to users and programs of the system. An operating system
performs basic tasks such as controlling and allocating memory, prioritizing
system requests, controlling input and output devices, facilitating computer networking and
managing files.
Common
contemporary desktop OSes are Linux, Mac
OS X, Microsoft Windows and Solaris.
Mac, Linux, and Windows all have server and personal variants. With the exception
of Microsoft Windows, the designs of each of the aforementioned OSs were
inspired by, or directly inherited from, the Unix operating system. Unix was
developed at Bell Labs beginning in the late 1960s and spawned
the development of numerous free and proprietary operating systems.
Operating
systems that can be found on mobile devices include Palm
OS, Windows Mobile, Familiar Linux, The
Ångström Distribution and Darwin (iPhone OS).
Linux
 |
| GNOME Linux desktop |
Linux is a Unix-like computer operating system. Linux is one of the most
prominent examples of free software and open source development: typically all underlying source code can be freely modified, used, and
redistributed by anyone.[13] The name "Linux" comes from
the Linux kernel, started in 1991 by Linus Torvalds. The system's utilities and libraries usually come from the GNU operating system,
announced in 1983 by Richard Stallman. The GNU contribution is the
basis for the alternative name GNU/Linux.[14]
Predominantly
known for its use in servers,
Linux is supported by corporations such as Dell, Hewlett-Packard, IBM, Novell, Oracle Corporation, Red
Hat,
and Sun Microsystems. It is used as an operating system
for a wide variety of computer hardware, including desktop computers, supercomputers,[15] video game systems, such as the PlayStation 3, several arcade games, and embedded devices such as mobile phones, routers, and stage lighting systems.
Mac
OS X
 |
| Mac
OS X desktop |
Mac OS X is a
line of graphical operating systems developed,
marketed, and sold by Apple Inc., the latest of which is pre-loaded on
all currently shipping Macintosh computers. Mac OS X is the successor to the original Mac
OS,
which had been Apple's primary operating system since 1984. Unlike its
predecessors, Mac OS X is a Unix-based operating
system[16] built on technology developed at NeXT from
the second half of the 1980s until early 1997, when Apple purchased the
company.
The server edition, Mac OS X Server, is architecturally very
similar to its desktop counterpart but usually runs on Apple's line of
Macintosh server hardware. It includes workgroup management and administration
software tools that provide simplified access to key network services, including a mail transfer agent, a Samba server, an LDAP server, a domain name server, and
others.
Microsoft Windows
 |
| Windows Vista operating system |
Microsoft
Windows is the name of several families of software operating systems by Microsoft.
Microsoft first introduced an operating environment named Windows in November
1985 as an add-on to MS-DOS in
response to the growing interest in graphical user interfaces (GUIs). The most recent
client version of Windows is Windows Vista. The
current server version of Windows is Windows Server 2008.
Applications
 |
| GIMP raster graphics editor |
Application
software employs the capabilities of a computer directly and thoroughly to a
task that the user wishes to perform. This should be contrasted with system software which is involved in integrating
a computer's various capabilities, but typically does not directly apply them
in the performance of tasks that benefit the user. In this context the term application refers to both the application software and its implementation. A
simple, if imperfect analogy in
the world of hardware would be the relationship of an electric light bulb (an
application) to an electric power generation plant (a system). The power plant
merely generates electricity, not itself of any real use until harnessed to an
application like the electric light that performs a service that benefits the
user.
Typical examples
of software applications are word processors, spreadsheets, and media players.
Multiple applications bundled together as a package are sometimes referred to
as an application suite. Microsoft Office and OpenOffice.org, which bundle together a word
processor, a spreadsheet, and several other discrete applications, are typical
examples. The separate applications in a suite usually have a user interface that has some commonality making
it easier for the user to learn and use each application. And often they may
have some capability to interact with each other in ways beneficial to the
user. For example, a spreadsheet might be able to be embedded in a word
processor document even though it had been created in the separate spreadsheet
application.
End-user development tailors systems to meet the user's specific needs. User-written software
include spreadsheet templates, word processor macros, scientific simulations,
graphics and animation scripts. Even email filters are a kind of user software.
Users create this software themselves and often overlook how important it is.
Lifetime
Most personal
computers are standardized to the point that purchased software is expected to
run with little or no customization for the particular computer. Many PCs are
also user-upgradeable, especially desktop and workstation class computers.
Devices such as main memory, mass storage, even the motherboard and central processing unit may
be easily replaced by an end user. This upgradeability is, however, not indefinite
due to rapid changes in the personal computer industry. A PC that was
considered top-of-the-line five or six years prior may be impractical to
upgrade due to changes in industry standards. Such a computer usually must be
totally replaced once it is no longer suitable for its purpose. This upgrade
and replacement cycle is partially related to new releases of the primary
mass-market operating system, which tends to drive the acquisition of new
hardware and render obsolete previously serviceable hardware (planned obsolescence).
References
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(1993). "Workstation". Encyclopedia of Computer Science (Third Edition). New York: Van Nostrand Reinhold. ISBN
0442276796.
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Units by 2014
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- Rugged PC leaders
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computer guide
- Smaller PCs Cause Worry for Industry - NYTimes.com
- New Windows Mobile 6 Devices :: Jun/Jul 2007
- pete
edge...casefancasefancase
- The NeXT computer introduced in 1988 did not include a floppy drive, which at the
time was unusual.
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Linux.org. Retrieved on 2007-07-06.
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Alex (2004). "1.1", Linux System Administrator's Guide,
version 0.9. Retrieved
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Retrieved on 2007-04-22.
- IDC: Consolidation to Windows won't happen
Source: http://en.wikipedia.org/wiki/Personal_computer
Published - September 2008
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