Personal Computer
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
contrasted with the batch processing or time-sharing models which allowed
larger, more expensive minicomputer and mainframe systems to be used by many
people, usually at the same time. Large data processing systems require a
full-time staff to operate efficiently.
Software applications
for personal computers include, but are not limited to, word processing,
spreadsheets, databases, Web browsers and e-mailclients, digital media
playback, 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.
Personal computers may be connected to a local area network (LAN), either by a
cable or a wireless connection. A personal computer may be a desktop computer
or a laptop,tablet, or a handheld PC.
Early PC owners usually
had to write their own programs to do anything useful with the machines, even
lacking an operating system. The very earliest microcomputers, equipped with a
front panel, required hand-loading of a bootstrap program to load programs from
external storage (paper tape, cassettes, or eventually diskettes). Before very
long, automatic booting from permanent read-only memory became universal.
Today's users have
access to a wide range of commercial software and freeware, which is provided
in ready-to-run or ready-to-compile form. Since the early 1990s, the Microsoft
Windows™ operating systems and Intel hardware have dominated much of the
personal computer market, first withMS-DOS and then with the "Wintel"
(Windows + Intel) combination. Popular alternatives to Microsoft's Windows
operating systems includeApple's Mac OS X and the free open-source Linux and
BSD operating systems. AMD provides the major alternative to Intel's central
processing units. Applications and games for PCs are typically developed and
distributed independently from the hardware or OS manufacturers, whereas
software for many mobile phones and other portable systems is approved and
distributed through a centralized online store.
In July and August
2011, marketing businesses and journalists began to talk about the 'Post-PC
Era', in which the desktop form factor was being replaced with more portable
computing such asnetbooks, notebooks, tablets, and smartphones.
History
The Programma 101,
released in 1965, was the first commercial "desktop computer",[4] but
today would usually be considered a printing programmable calculator.
In what was later to be
called The Mother of All Demos, SRI researcher Douglas Engelbart 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.
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.
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
Xerox Alto, developed in 1973 at Xerox's Palo Alto Research Center (PARC), had
a graphical user interface (GUI) that later served as inspiration for Apple
Computer's Macintosh, and Microsoft's Windowsoperating system. The Wang 2200 of
1973 had a full-size cathode ray tube (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. 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.
Minimal programming was done with toggle switches to enter instructions, and
output was provided by front panel lamps. Practical use required adding
peripherals such as keyboards, computer displays, disk drives, and printers.
Micral N was the earliest commercial, non-kit microcomputer based on a
microprocessor, the Intel 8008. It was built starting in 1972 and about 90,000
units were sold. 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 theCommodore PET introduced in
January 1977. It was soon followed by the Apple II (usually referred to as the
"Apple") in June 1977, and the TRS-80 from Radio Shack in November
1977. Mass-market ready-assembled computers allowed a wider range of people to
use computers, focusing more on software applications and less on development
of the processor hardware.
During the early 1980s,
home computers were further developed for household use, with software for
personal productivity, programming and games. They typically could be used with
a televisionalready in the home as the computer display, with low-detail blocky
graphics and a limited color range, and text about 40 characters wide by 25
characters tall. One such machine, theCommodore 64, totaled 17 million units
sold, making it the best-selling single personal computer model of all time.[5]
Another such computer, the NEC PC-98, sold more than 18 million units.[6]
Somewhat larger and
more expensive systems (for example, running CP/M), or sometimes a home
computer with additional interfaces and devices, although still low-cost
compared withminicomputers and mainframes, were aimed at office and small
business use, typically using "high resolution" monitors capable of
at least 80 column text display, and often no graphical or color drawing
capability.
Workstations were
characterized by high-performance processors and graphics displays, with large
local disk storage, networking capability, and running under a multitasking
operating system.
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. 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.
In 1982 "The
Computer" was named Machine of the Year by Time Magazine.
Market and sales
See also: Market share
of leading PC vendors
Personal computers
worldwide in million distinguished by developed and developing world
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. 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.[7]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.[8]
The global personal
computer shipments were 350.9 million units in 2010,[9] 308.3 million units in
2009[10] and 302.2 million units in 2008.[11][12] The shipments were 264
million units in the year 2007, according to iSuppli,[13] up 11.2 percent from
239 million in 2006.[14] In 2004, the global shipments were 183 million units,
an 11.6 percent increase over 2003.[15] In 2003, 152.6 million computers were
shipped, at an estimated value of $175 billion.[16]In 2002, 136.7 million PCs
were shipped, at an estimated value of $175 billion.[16] In 2000, 140.2 million
personal computers were shipped, at an estimated value of $226 billion.[16]
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.[17] In
1999, Asia had 14.1 million units shipped.[18]
For 2011, global PC shipments
are expected to reach 364 million units, a 3.8% growth comparing to 2010.[19]
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.[20][21]
Based on IDC data for
Q2 2011, for the first time China surpassed US in PC shipments by 18.5 million
and 17.7 million respectively. It is reflects the rising of emerging markets as
well as the relative stagnation of mature regions.[22]
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.[23] 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.[24]
Deloitte consulting
firm predicted that in 2011, smartphones and tablet computers as computing
devices would surpass the PCs sales.[25]
Average selling price
Selling prices of
personal computers, unlike other consumer commodities, steadily declined due to
lower costs of production and manufacture. Capabilities of the computers also
increased. In 1975, an Altair kit sold for only around US $400, but required
customers to solder components into circuit boards; peripherals required to
interact with the system in alphanumeric form instead of blinking lights would
add another $2000, and the resultant system was only of use to hobbyists.[26]
At their introduction
in 1981, the US $1,795 price of the Osborne 1 and its competitor Kaypro was
considered an attractive price point; these systems had text-only displays and
only floppy disks for storage. By 1982, Michael Dell observed that a personal
computer system selling at retail for about $3,000 US was made of components
that cost the dealer about $600; typical gross margin on a computer unit was
around $1,000.[27] The total value of personal computer purchases in the US in
1983 was about $4 billion, comparable to total sales of pet food. By late 1998,
the average selling price of personal computer systems in the United States had
dropped below $1000.[28]
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.[29] 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.[30]
Types
Stationary
Workstation
Sun SPARCstation 1+, 25
MHz RISCprocessor from early 1990s
Main article:
Workstation
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
modeling, computation-intensive scientific and engineering calculations, image processing,
architectural modeling, and computer graphics for animation and motion picture
visual effects.[31]
Desktop computer
Main article: Desktop
computer
Dell OptiPlex desktop
computer
Prior to the wide
spread usage of PCs, a computer that could fit on a desk was 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.
Gaming Computer
Main article: Gaming
computer
A gaming computer is a
standard desktop computer that typically has high-performance hardware, such as
a more powerful video card, processor, and memory, in order to handle the
requirements of demanding video games. A number of companies, such as
Alienware, manufacture prebuilt gaming computers, and companies such as Razer
and Logitech market mice, keyboards, and headsets geared towards gamers.
Single unit
Further information:
All-in-one computer
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.
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). The product line features the new Intel Atom
processor which specially enables them to consume less power and to be built
into small enclosures.
Home theater PC
Main article: Home
theater PC
Antec Fusion V2 home
theater PC withkeyboard 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 atelevision 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 MythTV, Windows
Media Center, GB-PVR,SageTV, Famulent or LinuxMCE. More recently, home theatre
PCs have been given the ability to connect to services that play movies and TV
shows on demand.
Mobile
Laptop
Main article: Laptop
A modern laptop
computer
A laptop computer or
simply laptop, also called a notebook computer, 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. 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. For this reason, Desktop
or Gaming computers are generally preferred to laptop PCs for gaming purposes.
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. 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. 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 replacement
Main article: Desktop
replacement computer
An Acer 18'4 inch
screen Desktop Replacement Laptop
A desktop replacement
computer (DTR) is a personal computer that provides the full capabilities of a
desktop computer while remaining mobile. They are often larger, bulkier
laptops. Because of their increased size, this class of computer usually
includes more powerful components and a larger display than generally used in
smaller portable computers and can have a relatively limited battery capacity
(or none at all). Some use a limited range of desktop components to provide
better performance at the expense of battery life. These are sometimes called
desknotes, a portmanteau of the words "desktop" and
"notebook," though the term is also applied to desktop replacement
computers in general.[32]
Netbook
Main article: Netbook
An HP netbook
Netbooks (also called
mini notebooks or subnotebooks) are a rapidly evolving[33] 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.[33] Walt
Mossberg called them a "relatively new category of small, light,
minimalist and cheap laptops."[34] By August 2009, CNET called netbooks
"nothing more than smaller, cheaper notebooks.".[33]
Initially, their
primary defining characteristic was the lack of an optical disc drive,
requiring it to be a separate and external device. This has become less
important as flash memory devices have gradually increased in capacity,
replacing the writable optical disc (e.g. CD-RW, DVD-RW) as a transportable
storage medium.
At their inception in
late 2007 — as smaller notebooks optimized for low weight and low cost[35] —
netbooks omitted key features (e.g., the optical drive), featured smaller
screens and keyboards, and offered reduced specification and computing power.
Over the course of their evolution, netbooks have ranged in size from below 5
in[36] to over 13 in,[37] and from ~1 kg (2-3 pounds). Often significantly less
expensive than other laptops,[38] by mid-2009, netbooks had been offered to
users "free of charge", with an extended service contract purchase of
a cellular data plan.[39]
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."[33]
Tablet PC
Main article: Tablet computer
HP Compaq tablet PC
with rotating/removable keyboard.
A tablet PC is a
notebook or slate-shaped mobile computer. 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. Recently, tablet PCs have been given
operating systems normally used on phones, like Android or iOS. This gives them
many of the same uses as a phone, but with more power and functionality.
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, andSamsung,
among others. Current UMPCs typically feature the Windows XP, Windows Vista,
Windows 7, or Linux operating system and low-voltage Intel Atom orVIA C7-M
processors.
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.
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 and thus actually represent a smartphone.
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.[40]
Hardware
An exploded view of a
modern personal computer and peripherals:
1. Scanner
2. CPU (Microprocessor)
3. Primary storage (RAM)
4. Expansion cards (graphics cards, etc.)
5. Power supply
6. Optical disc drive
7. Secondary storage (Hard disk)
8. Motherboard
9. Speakers
10. Monitor
11. System software
12. Application software
13. Keyboard
14. Mouse
15. External hard disk
16. Printer
Main article: Personal
computer hardware
Mass-market consumer
computers use highly standardized components and so are simple for an end user
to assemble into a working system. A typical desktop computer consists of a computer
case which holds the power supply, motherboard, hard disk and often an optical
disc drive. External devices such as a computer monitoror visual display unit,
keyboard, and a pointing device are usually found in a personal computer.
The motherboard connects
all processor, memory and peripheral devices together. The RAM, graphics card
and processor are mounted directly onto the motherboard. Thecentral processing
unit microprocessor chip plugs into a socket. Expansion memory plugs into
memory sockets. Some motherboards have the video display adapter, sound and
other peripherals integrated onto the motherboard. Others use expansion slots
for graphics cards, network cards, or other I/O devices. Disk drives for mass
storage are connected to the mother board with a cable, and to the power supply
through another cable. Usually disk drives are mounted in the same case as the
motherboard; formerly, expansion chassis were made for additional disk storage.
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 keyboard and the
mouse are external devices plugged into the computer through connectors on an
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.
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 PCIexpansion 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.
Toxic chemicals, such
as lead and mercury, are found in certain pieces of PC hardware. Lead is found
in the Cathode ray tube (CRT), which is located inside the monitor, as well as
in the Printed circuit board. While daily PC users are not exposed to these
toxic elements, danger arises in computer recycling, and thus stems the
controversy of electronic waste (e-Waste). The process of computer recycling
involves workers responsible for manually breaking down computers, which leads
to inevitable exposure to these toxic chemicals and serious health issues. Lead
is known to cause damage to the central nervous system, kidneys, and slow down
child brain development.Mercury, another toxic element found in PCs, is located
in the screen's fluorescent lamp, laser light generators in the optical disk
drive, and in mercury batteries in the circuit board and expansion cards. Even
the smallest amount of mercury, if it is inhaled or digested can cause serious
brain damage. Other chemicals found in PCs are cadmium, chromium, Polyvinyl
chloride (PVC), and barium, which are also found in the motherboard and other
crucial pieces of the computer. In each individual computer, about 17% of the
computer is lead,copper, zinc, mercury, and cadmium, 23% is plastic (which
usually gets burned and causes extreme air pollution), and 14% is Aluminiumand
20% is Iron (the last two do not cause extreme health risks, however they are
natural elements and do not decompose, which means they continue to take up
space unless they are recycled into new computers). Although there is not a
huge amount of these hazardous chemicals in each individual computer, even the
smallest amount of lead or mercury can ruin a community’s drinking water, or
cause serious brain damage.
Computer case
Main article: 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 or aluminum, although other materials such as wood and
plastic have been used. 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.
Power supply unit
Main article: Power
supply unit (computer)
Computer power supply
unit with top cover removed.
The power supply unit
converts general purpose electric current from the mains to direct current for
the other components of the computer.
Processor
Main article: Central
processing unit
AMD Athlon 64 X2 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 Motorola680x0 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 switched again, this time to x86-compatible processors by
Intel. Modern CPUs are equipped with a fan attached via heat sink.
Motherboard
Main article:
Motherboard
A motherboard without
processor, memory and extension cards, cables
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
Main article: Primary
storage
1GB DDR SDRAM PC-3200
module
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. Which exact kind depends on cost/performance issues at
any particular time. Main memory is much faster than mass storage devices like
hard disksor 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
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. 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. 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.
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
Main article: Visual
display unit
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. The word "monitor" is used in other contexts;
in particular in television broadcasting, where atelevision picture is
displayed to a high standard on a broadcast reference monitor. 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 Expansion card, there is circuitry to convert internaldata 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.
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 inputting 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. 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 achieved by pressing multiple keys at once or
in succession, such as inputting characters with accents or opening a task
manager. Programs use keyboard shortcuts 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.
Mouse
Main article: Mouse
(computing)
Computer mice built
between 1986 and 2007
A Mouse on a computer
is a small, slideable 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. 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(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.
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 maintenance free. They
work on a wider variety of surfaces and can even operate on walls, ceilings or
other non-horizontal surfaces.
Other components
Proper ergonomic design
of personal computer workplace is necessary to prevent repetitive strain
injuries, which can develop over time and can lead to long-term disability.[41]
Mass storage
All computers require
either fixed or removable storage for their operating system, programs and user
generated material.
Formerly the 5¼ inch
and 3½ 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.[note
1]
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
manufacturing costs dropped, by the mid 1980s.
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
storage, but typically it is on a hard disks. A Live CD is the running of an OS
directly from a CD. While this is slow compared to storing the OS on a hard
drive, it is typically used for installation of operating systems,
demonstrations, system recovery, or other special purposes. Large flash memory
is currently more expensive than hard drives of similar size (as of mid-2008)
but are starting to appear in laptop computers because of their low weight,
small size and low power requirements.
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
Main article: Computer
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.[42] The term
includes application software such as word processors which perform productive
tasks for users, system software such as operating systems, which interface
with computer 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 gameplay 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 softwarewritten primarily for
personal computers tends to be designed with simplicity of use, or "user-friendliness"
in mind. However, the software industrycontinuously provide a wide range of new
products for use in personal computers, targeted at both the expert and the
non-expert user.
Operating system
Main article: Operating
system
See also: Usage share
of operating systems
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 OSs are Microsoft Windows, Mac OS X, Linux, Solaris and FreeBSD.
Windows, Mac, and Linux 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.
Microsoft Windows
Main article: Microsoft
Windows
Microsoft Windows is
the collective brand name of several 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)[43][44] generated by Apple's 1984 introduction of the
Macintosh. The most recent client version of Windows is Windows 7 and Windows
Server 2008 R2 which was available at retail on October 22, 2009.
OS X
Main article: OS X
OS X (formerly Mac OS
X) is a line of operating systems developed, marketed, and sold by Apple Inc..
OS X is the successor to the original Mac OS, which had been Apple's primary
operating system since 1984. OS X is a Unix-based graphical operating system. The
most recent version of OS X is OS X Mountain Lion.
AmigaOS
Main article: AmigaOS
AmigaOS is the default
native operating system of the Amiga personal computer. It was developed first
by Commodore International, and initially introduced in 1985 with the Amiga
1000. Early versions (1.0-3.9) run on the Motorola 68k series of 16-bit and
32-bit microprocessors, while the newer AmigaOS 4 runs only on PowerPC
microprocessors. On top of a preemptive multitasking kernel called Exec, it
includes an abstraction of the Amiga's unique hardware, a disk operating system
called AmigaDOS, a windowing system API called Intuition and a graphical user
interface called Workbench. A command line interface called AmigaShell is also
available and integrated into the system. The GUI and the CLI complement each
other and share the same privileges. The current holder of the Amiga
intellectual properties is Amiga Inc. They oversaw the development of AmigaOS 4
but did not develop it themselves, contracting it instead to Hyperion Entertainment.
On 20 December 2006, Amiga Inc terminated Hyperion's license to continue
development of AmigaOS 4. However, in 30 September 2009, Hyperion was granted
an exclusive, perpetual, worldwide right to AmigaOS 3.1 in order to use,
develop, modify, commercialize, distribute and market AmigaOS 4.x and
subsequent versions of AmigaOS (including AmigaOS 5).
Linux
Main article: Linux
A Linux distribution
running KDE Plasma Desktop.
Linux is a family of
Unix-like computer operating systems. 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.[45] 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.[46]
Known for its use in
servers as part of the LAMP application stack, Linux is supported by
corporations such as Dell, Hewlett-Packard, IBM, Novell,Oracle Corporation, Red
Hat, Canonical Ltd. and Sun Microsystems. It is used as an operating system for
a wide variety of computer hardware, including desktop computers, netbooks,
supercomputers,[47] video game systems, such as the PlayStation 3, several
arcade games, and embedded devices such as mobile phones, portable media
players, routers, and stage lighting systems.
Applications
A computer user will
apply application software to carry out a specific task. System software
supports applications and provides common services such as memory management,
network connectivity, or device drivers; all of which may be used by
applications but which are not directly of interest to the end user. 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.
Electronic waste
Personal computers can
become a large contributor to the 50 million tons of waste of discarded
electronic goods that is being generated annually, according to the United
Nations Environment Programme. To solve the electronic waste issue affecting
developing countries and the environment, an Extended producer responsibility
act was implemented. Organizations, such as the Silicon Valley Toxics
Coalition, Basel Action Network, Toxics Link India, SCOPE, and Greenpeace
contribute to the strategy. The Silicon Valley Toxics Coalition and BAN (Basel
Action Network) teamed up with 32 electronic recyclers in the US and Canada to
create an e-steward program due to the lack of national legislation and
regulation for the exporting and importing of electronic waste. The creation of
an e-steward program created another option for manufacturers and customers to
dispose of their electronic waste properly. The Silicon Valley Toxics Coalition
founded the Electronics TakeBack Coalition, which is a coalition that advocates
for the production of environmentally friendly products. The TakeBack Coalition
works with policy makers, recyclers, and smart businesses to get manufacturers
to take full responsibility of their products. There are organizations opposing
EPR, such as the Reason Foundation opposes the EPR for two main reasons. The
first reason is that the EPR relies on the idea that is the manufacturers pay
for the harm they do to the environment, they will learn their lesson. The
second reason is that the EPR assumes the current design practices are
environmentally inefficient. The Reason Foundation claims that manufacturers
are moving toward reduced material use and energy use instead.
Terminator 3: Rise of
the Machines adalah film fiksi
ilmiah yang disutradarai oleh Jonathan Mostow, dan
dibintangi oleh Arnold Schwarzenegger, Nick Stahl, Claire Danes, dan Kristanna Loken. Film ini ditayangkan secara serentak di Indonesia pada bulan Juli 2003.
