2. The Information-Processing MachineLike the Analytical
Engine, the computer is a machine that changesinformation from one
form to another. All computers take ininformation (input) and give
out information (output).The computers flexibility isnt hidden in
hardwarethe physicalparts of the computer system. The secret is
software, or programsthe instructions that tell the hardware what
to do to transformthe input data (information in a form that it can
read) into thenecessary output.Evolution and AccelerationComputer
hardware evolved rapidly, with new technologies replacingold every
few years. People sometimes refer to four generations ofcomputers
based on the vacuum tube, the transistor, the integratedcircuit,
and the microprocessor. Each of these new technologiesresulted in
computer systems that were more reliable, smaller,faster, more
efficient, and cheaper.Moores Law in 1965 predicted that the power
of a silicon chip ofthe same size would double about every 18
months; this predictionhas been remarkably accurate ever
since.
3. The Microcomputer RevolutionA microprocessor contains the
critical components of a computer on asilicon chip. Thanks to the
microprocessor, the microcomputerrevolution began in the mid-1970s
with the introduction of low-cost,typewriter-sized computers as
powerful as many of the room-sizedcomputers that had come
before.Personal computers, or PCs, as microcomputers have come to
beknown, are now everyday tools in offices, factories, homes,
andschools.Mainframes and SupercomputersBefore the microcomputer
revolution, most information processingwas done on mainframe
computersroom-sized machines withprice tags that matched their
size. Today, large organizations still usemainframes for big
computing jobs.Travel agents and bank tellers communicate with a
mainframe usinga computer terminala combination keyboard and screen
thattransfers information to and from the computer.
Mainframecomputers are capable of communicating with several
userssimultaneously through a technique called timesharing.
4. Workstations and PCsServers are computers especially
designed to provide software andother resources to other computers
over a network.A workstation is a high-end desktop computer with
thecomputing power of a minicomputer at a fraction of the
cost.Workstations are widely used by scientists, engineers, Wall
Streetanalysts, animators, and others whose work involves
intensivecomputation. Personal computers are less powerful and
lessexpensive than workstations, but the line between the
twocategories is growing blurry.
5. Portable ComputersToday, one of the fastest growing segments
of the PC marketinvolves machines that arent tied to the
desktopportablecomputers. Portability is a relative
term.Flat-screen, battery-powered laptop computers are light enough
torest on your lap while you work or carry like a small briefcase
whenclosed.Embedded Computers and Special-Purpose ComputersNot all
computers are general-purpose machines. Many are special-purpose
(dedicated) computers that perform specific tasks,ranging from
controlling the temperature and humidity in a high-rise office
building to monitoring your heart rate while you work out.Embedded
computers enhance all kinds of consumer goods:wristwatches, game
machines, stereos, videocassette recorders(VCRs), ovens, and even
automobiles. Embedded computers are alsowidely used in industry,
the military, and science for controlling avariety of hardware
devices, including robots.When a program is immortalized on a
silicon chip it becomesfirmwarea hybrid of hardware and
software.
6. COMPUTER CONNECTIONSTHE INTERNET REVOLUTIONWhile the world
was still reeling from the impact of themicrocomputer revolution,
another information technologyrevolution was quietly building up
steam: a network revolution.If current trends continue, well look
back on the 1990s as theend of the personal computing era and the
beginning of theinterpersonal computing era.The Emergence of
NetworksThe first computers were large, expensive,
self-containedmachines that could process only one job at a time.
Theinvention of timesharing in the 1960s allowed multiple users
toconnect to a single mainframe computer through
individualterminals. When personal computers started
replacingterminals, they were often linked together in local
areanetworks so they could share scarce, expensive resources.
7. The Internet ExplosionA few visionary computer scientists
and engineers, with financialbacking from the U.S. government,
built an experimental networkcalled ARPANET in 1969. This
groundbreaking network wouldbecome the Internetthe global
collection of networks that isradically transforming the way the
world uses computers.Electronic mail (e-mail) made it possible for
even casual computerusers to send messages.In its early years the
Internet was the domain of researchers,academics, and government
officials. In the 1990s Internetsoftware took giant leaps forward
in usability. The biggest changescame with the development of the
World Wide Web, a vast tractof the Internet with a multimedia
landscape incorporatingpictures, sounds, animation, and even
video.Web sites designed as first-stop gateways for Internet
surfers arecalled portals. These are often associated with search
engines.
8. THE INTERNET CULTUREToday, all kinds of people are signing
onto the Internet in recordnumbers. They use it to communicate with
each other, do research,download music, shop, study, browse, and
publish their own work.Many companies now have intranets private
organizationalnetworks based on Internet technology. Intranets
allow people totransmit, share, and store information within an
enterprise. Severalcompanies are marketing stripped-down computers
designed tofunction mainly as network terminals, often called
networkcomputers or information appliances. These allow people
toconnect to the Internet without needing a full-blown
personalcomputer
9. Explanations: Clarifying TechnologyApplicationsMany people
define computer literacy as the ability to usecomputers.
Application programs, also known simply asapplications, are the
software tools that allow a computer to beused for specific
purposes:Word processing and desktop publishing: Word processing
skill iscritical for anyone who communicates in writing. Its by far
theapplication used most by students. Desktop publishing uses
thepersonal computer to transform written words into
polished,visually exciting publications.Spreadsheets and other
number-crunching applications: Inbusiness the electronic
spreadsheet is the personal computerapplication that pays the rent,
or at least calculates it.Databases for information storage and
retrieval: If wordprocessors and spreadsheets are the most popular
PCapplications, databases reign supreme in the world
ofmainframes.
10. Databases for information storage and retrieval: If
wordprocessors and spreadsheets are the most popular
PCapplications, databases reign supreme in the world ofmainframes.
Computer graphics: Computers are able to produce all kinds
ofgraphics, from the charts and graphs produced by spreadsheetsto
realistic 3-D animation. Multimedia and hypermedia: Multimedia
tools for PCs make itpossible to combine audio and video with
traditional text andgraphics, adding new dimensions to computer
communication.Hypermedia tools focus on the interactive
capabilities ofcomputers, allowing users to explore a variety of
paths throughinformation sources.
11. Telecommunication and networking: Every day morecomputers
are connected networked so they cansend information back and forth;
were entering an erawhen networking is the norm. Many experts
believe thattelecommunicationlong-distance communicationwillbethe
single most important function of computers in thenot-too-distant
future. Artificial intelligence: Artificial intelligence is
thebranch of computer science that explores usingcomputers in tasks
that require intelligence,imagination, and insighttasks that have
traditionallybeen performed by people rather than machines. General
problem solving: People use computers to solveproblems. Programming
languages arent applications;theyre tools that allow you to build
and customize
12. Implications: Social and Ethical IssuesThe immediate
potential risks of the computer revolutionare:The threat to
personal privacy posed by large databasesThe hazards of high-tech
crime and the difficulty ofkeeping data secureThe difficulty of
defining and protecting intellectualpropertyThe risks of failure of
computer systemsThe threat of automation and the dehumanisation
ofworkThe abuse of information as a tool of political andeconomic
powerThe dangers of dependence on complex technology
13. The longer-term potential risks of the computerrevolution
include:The death of privacyThe blurring of realityThe evolution of
intelligence
14. END OF CH3
15. CH 4 COMPUTER HARDWARE
16. The four basic hardware components of every computer
systemare described below.1. Input devices accept input from the
outside world. The mostcommon input device is the keyboard. Other
input devices includepointing devices like a mouse and joysticks.2.
Output devices send information to the outside world. Mostcomputers
use a TV-like video monitor as their main outputdevice and some
kind of printer for producing paper printouts.3. A processor, or
central processing unit (CPU), processesinformation, performing all
the necessary arithmetic calculationsand making basic decisions
based on information values.4. Storage devices and memory are used
to store information.The most common storage devices are disk
drives and tape drives.Different types of memory are used for
different long-term andshort-term storage tasks.
17. Bits, Bytes, and BuzzwordsByte: a grouping of 8 bits.K
(kilobyte) (someatimes called KB): about 1000 bytesof
information.MB (megabyte) (sometimes called meg):approximately 1000
K, or 1 million bytes.GB (gigabyte) (sometimes called gig):
approximately1000 megabytes.TB (terabyte): approximately 1 million
megabytes.
18. THE COMPUTERS CORE : THE CPU AND MEMORYThe CPU : The Real
ComputerA modern CPU is an extraordinarily complexcollection of
electronic circuits When all of thosecircuits are built into a
single silicon chip, as theyare in most computers today, that chip
is referred toas a microprocessor. In a typical desktop
computer,the CPU is housed along with other chips andelectronic
components on a circuit board.Compatibility. Not all software is
compatible withevery CPU; that is, software written for
oneprocessor may not work with another.
19. Speed. A computers speed is determined in part bythe speed
of its internal clockthe timing device thatproduces electrical
pulses to synchronize thecomputers operations. Computers are often
describedin terms of their clock speeds, measured in unitscalled
megahertz. Speed is also determined by thearchitecture of the
processorthe design thatdetermines how individual components of the
CPU areput together on the chip.Parallel processing puts more than
one processor ina computer.
20. The Computers MemoryRAM (random access memory) is the most
common type ofprimary storage, or computer memory. RAM chips
containcircuits that can be used to store program instructions
anddata temporarily. You can store a piece of information in anyRAM
locationyou can pick one at randomand thecomputer can, if so
instructed, quickly retrieve it.RAM is called volatile memory
because information storedthere is not held permanently.The
computer also has nonvolatile memory called ROM(read-only memory)
because the computer can only readinformation from it; it can never
write any new informationon it. ROM isnt always hidden away on
chips inside thecomputers chassis. Many home video game machines
andhome computers use removable ROM cartridges aspermanent storage
devices for games and other programs.
21. Buses, Ports, and PeripheralsInformation travels between a
computers componentsthrough groups of wires called buses. Buses
typicallyhave 8, 16, or 32 wires; a bus with 16 wires is called
a16-bit bus because it can transmit 16 bits ofinformation at
oncetwice as many as an 8-bit bus.Some buses connect to expansion
slots inside thecomputers housing. Users can customize
theircomputers by inserting special-purpose circuit boards(usually
called cards or just boards) into these slots.
22. Reading ToolsOptical-mark readers use reflected light
todetermine the location of pencil marks onstandardized test answer
sheets and similar forms. Bar-code readers use light to read
universalproduct codes (UPCs), inventory codes, and othercodes
created out of patterns of variable-width bars. Magnetic-ink
character readers read those odd-shaped numbers printed with
magnetic ink onchecks. In many stores bar-code readers are attached
topoint-of-sale (POS) terminals. These terminalssend information
scanned by the wand to amainframe computer.
23. Digitizing the Real WorldA scanner is an input device that
can make a digital representationof any printed image. A digital
camera can be used to capture snapshots of the realworld as digital
images. Audio digitizers contain circuitry to digitize sounds
frommicrophones and other audio devices. A video digitizer is a
collection of circuits that can capture inputfrom a video source
and convert it to a digital signal that can bestored in memory and
displayed on computer screens.Sensing devices designed to monitor
temperature, humidity,pressure, and other physical quantities
provide data used inrobotics, environmental climate control,
weather forecasting,medical monitoring, biofeedback, scientific
research, and hundredsof other applications.
24. STORAGE DEVICES: INPUT MEETS OUTPUTTape drives are common
storage devices on most mainframe computersand some personal
computers. The reason for the widespread use ofmagnetic tape as a
storage medium is because a typical magnetic tape canstore massive
amounts of information in a small space at a relatively lowcost.
Magnetic tape has one clear limitation: Tape is a sequential
accessmedium. Because retrieving information from the middle of a
tape is time-consuming, magnetic tape is used today mostly for
backup of data and a fewother operations that arent time
sensitive.
25. Magnetic DisksThe magnetic disk is a readily available
alternative to tape as astorage medium: A computers disk drive can
rapidly retrieveinformation from any part of a magnetic disk
without regard to theorder in which the information was recorded.A
diskette (or floppy disk) is a small, magnetically
sensitive,flexible plastic wafer housed in a plastic case, used to
transferinformation between machines and for packaging
commercialsoftware.A hard disk is a rigid, magnetically sensitive
disk that spins rapidlyand continuously inside the computer chassis
or in a separate boxconnected to the computer housing; the user
never removes this typeof hard disk.There are several choices of
removable media to fill the gap betweenlow-capacity, slow diskettes
and nonremovable, fast hard drives:
26. Optical DisksFor multimedia applications, optical disks
provide a storagealternative to hard disks.An optical disk drive
uses laser beams rather than magnets to readand write bits of
information on the disk surface. While they currentlyarent as fast
as hard disks, optical disks have considerably more roomfor storing
data.CD-ROM (compact discread-only memory) drives are opticaldrives
capable of reading CD-ROMsdata disks that are physicallyidentical
to musical compact discs. Because CD-ROMs are read-onlydevices,
they cant be used as secondary storage devices. CD-RW(compact disc
rewritable) drives can write, erase, and rewrite CDs.DVD-ROMs
(digital versatile disk-read-only memory) willprobably replace
CD-ROMs for multimedia applications because oftheir enormous
capacity.
27. Solid-State Storage DevicesFlash memory is a type of
erasable memory chip thatcan serve as a reliable, low-energy,
quiet, compactalternative to disk storage. Most experts believe
thatsolid state storage technology like flash memory willeventually
replace disk and tape storage.