The document provides an overview of the evolution of computers from the earliest information processing machines to modern personal computers and networks. It discusses: 1) How early computers took input and produced output but relied on software to direct hardware operations. 2) How computer hardware evolved rapidly through generations using different technologies like vacuum tubes, transistors, integrated circuits and microprocessors making computers smaller, faster and cheaper. 3) How the microprocessor revolutionized computing by enabling the development of microcomputers and personal computers. 4) How networks emerged allowing multiple users to access mainframe computers and later connect personal computers, leading to the Internet revolution.

1. IS 202
Ch 03- Computer Evolution

2. The Information-Processing Machine
Like the Analytical Engine, the computer is a machine that changes
information from one form to another. All computers take in information
(input) and give out information (output).
The computer’s flexibility isn’t hidden in hardware—the physical parts
of the computer system. The secret is software, or programs—the
instructions that tell the hardware what to do to transform the input data
(information in a form that it can read) into the necessary output.
Evolution and Acceleration
Computer hardware evolved rapidly, with new technologies replacing old
every few years. People sometimes refer to four generations of
computers based on the vacuum tube, the transistor, the integrated
circuit, and the microprocessor. Each of these new technologies resulted
in computer systems that were more reliable, smaller, faster, more
efficient, and cheaper.
Moore’s Law in 1965 predicted that the power of a silicon chip of the
same size would double about every 18 months; this prediction has
been remarkably accurate ever since.

3. The Microcomputer Revolution
A microprocessor contains the critical components of a computer on a
silicon chip. Thanks to the microprocessor, the microcomputer
revolution began in the mid-1970s with the introduction of low-cost,
typewriter-sized computers as powerful as many of the room-sized
computers that had come before.
Personal computers, or PCs, as microcomputers have come to be
known, are now everyday tools in offices, factories, homes, and schools.
Mainframes and Supercomputers
Before the microcomputer revolution, most information processing was
done on mainframe computers—room-sized machines with price tags
that matched their size. Today, large organizations still use mainframes
for big computing jobs.
Travel agents and bank tellers communicate with a mainframe using a
computer terminal—a combination keyboard and screen that transfers
information to and from the computer. Mainframe computers are capable
of communicating with several users simultaneously through a technique
called timesharing.

4. Workstations and PCs
Servers are computers especially designed to provide software and
other resources to other computers over a network.
A workstation is a high-end desktop computer with the computing
power of a minicomputer at a fraction of the cost. Workstations are
widely used by scientists, engineers, Wall Street analysts, animators,
and others whose work involves intensive computation. Personal
computers are less powerful and less expensive than workstations, but
the line between the two categories is growing blurry.

5. Portable Computers
Today, one of the fastest growing segments of the PC market involves
machines that aren’t tied to the desktop—portable computers.
Portability is a relative term.
Flat-screen, battery-powered laptop computers are light enough to rest
on your lap while you work or carry like a small briefcase when closed.
Embedded Computers and Special-Purpose Computers
Not 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 also
widely used in industry, the military, and science for controlling a variety
of hardware devices, including robots.
When a program is immortalized on a silicon chip it becomes
firmware—a hybrid of hardware and software.

6. COMPUTER CONNECTIONS
THE INTERNET REVOLUTION
While the world was still reeling from the impact of the
microcomputer revolution, another information technology
revolution was quietly building up steam: a network revolution. If
current trends continue, we’ll look back on the 1990s as the end of
the personal computing era and the beginning of the interpersonal
computing era.
The Emergence of Networks
The first computers were large, expensive, self-contained machines
that could process only one job at a time. The invention of
timesharing in the 1960s allowed multiple users to connect to a
single mainframe computer through individual terminals. When
personal computers started replacing terminals, they were often
linked together in local area networks so they could share scarce,
expensive resources.

7. The Internet Explosion
A few visionary computer scientists and engineers, with financial
backing from the U.S. government, built an experimental network
called ARPANET in 1969. This groundbreaking network would become
the Internet—the global collection of networks that is radically
transforming the way the world uses computers. Electronic mail (e-
mail) made it possible for even casual computer users to send
messages.
In its early years the Internet was the domain of researchers,
academics, and government officials. In the 1990s Internet software
took giant leaps forward in usability. The biggest changes came with
the development of the World Wide Web, a vast tract of the Internet
with a multimedia landscape incorporating pictures, sounds,
animation, and even video.
Web sites designed as first-stop gateways for Internet surfers are
called portals. These are often associated with search engines.

8. THE INTERNET CULTURE
Today, all kinds of people are signing onto the Internet in record
numbers. 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 organizational networks based
on Internet technology. Intranets allow people to transmit, share, and
store information within an enterprise. Several companies are marketing
stripped-down computers designed to function mainly as network
terminals, often called network computers or information appliances.
These allow people to connect to the Internet without needing a full-
blown personal computer

9. Explanations: Clarifying Technology
Applications
Many people define computer literacy as the ability to use computers.
Application programs, also known simply as applications, are the
software tools that allow a computer to be used for specific purposes:
Word processing and desktop publishing: Word processing skill is
critical for anyone who communicates in writing. It’s by far the
application used most by students. Desktop publishing uses the
personal computer to transform written words into polished, visually
exciting publications.
Spreadsheets and other number-crunching applications: In business
the electronic spreadsheet is the personal computer application that
pays the rent, or at least calculates it.
Databases for information storage and retrieval: If word processors
and spreadsheets are the most popular PC applications, databases
reign supreme in the world of mainframes.

10. Databases for information storage and retrieval: If word processors
and spreadsheets are the most popular PC applications, databases
reign supreme in the world of mainframes.
• Computer graphics: Computers are able to produce all kinds of
graphics, from the charts and graphs produced by spreadsheets to
realistic 3-D animation.
• Multimedia and hypermedia: Multimedia tools for PCs make it
possible to combine audio and video with traditional text and
graphics, adding new dimensions to computer communication.
Hypermedia tools focus on the interactive capabilities of computers,
allowing users to explore a variety of paths through information
sources.

11. • Telecommunication and networking: Every day more
computers are connected — networked — so they can
send information back and forth; we’re entering an era
when networking is the norm. Many experts believe that
telecommunication—long-distance communication—will be
the single most important function of computers in the not-
too-distant future.
• Artificial intelligence: Artificial intelligence is the branch of
computer science that explores using computers in tasks
that require intelligence, imagination, and insight—tasks
that have traditionally been performed by people rather than
machines.
• General problem solving: People use computers to solve
problems. Programming languages aren’t applications;
they’re tools that allow you to build and customize
applications.

12. Implications: Social and Ethical Issues
The immediate potential risks of the computer revolution
are:
The threat to personal privacy posed by large databases
The hazards of high-tech crime and the difficulty of keeping
data secure
The difficulty of defining and protecting intellectual property
The risks of failure of computer systems
The threat of automation and the dehumanisation of work
The abuse of information as a tool of political and economic
power
The dangers of dependence on complex technology

13. The longer-term potential risks of the computer
revolution include:
The death of privacy
The blurring of reality
The evolution of intelligence

14. END OF CH3

15. CH 4 COMPUTER HARDWARE

16. The four basic hardware components of every computer system are
described below.
1. Input devices accept input from the outside world. The most
common input device is the keyboard. Other input devices include
pointing devices like a mouse and joysticks.
2. Output devices send information to the outside world. Most
computers use a TV-like video monitor as their main output device
and some kind of printer for producing paper printouts.
3. A processor, or central processing unit (CPU), processes
information, performing all the necessary arithmetic calculations and
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 and short-
term storage tasks.

17. Bits, Bytes, and Buzzwords
Byte: a grouping of 8 bits.
K (kilobyte) (someatimes called KB): about 1000 bytes of
information.
MB (megabyte) (sometimes called meg): approximately
1000 K, or 1 million bytes.
GB (gigabyte) (sometimes called gig): approximately
1000 megabytes.
TB (terabyte): approximately 1 million megabytes.

18. THE COMPUTERS CORE : THE CPU AND MEMORY
The CPU : The Real Computer
A modern CPU is an extraordinarily complex collection
of electronic circuits When all of those circuits are built
into a single silicon chip, as they are in most
computers today, that chip is referred to as a
microprocessor. In a typical desktop computer, the
CPU is housed along with other chips and electronic
components on a circuit board.
Compatibility. Not all software is compatible with
every CPU; that is, software written for one processor
may not work with another.

19. Speed. A computer’s speed is determined in part by the
speed of its internal clock—the timing device that
produces electrical pulses to synchronize the computer’s
operations. Computers are often described in terms of
their clock speeds, measured in units called megahertz.
Speed is also determined by the architecture of the
processor—the design that determines how individual
components of the CPU are put together on the chip.
Parallel processing puts more than one processor in a
computer.

20. The Computer’s Memory
RAM (random access memory) is the most common type of
primary storage, or computer memory. RAM chips contain
circuits that can be used to store program instructions and data
temporarily. You can store a piece of information in any RAM
location—you can pick one at random—and the computer can, if
so instructed, quickly retrieve it.
RAM is called volatile memory because information stored
there is not held permanently.
The computer also has nonvolatile memory called ROM (read-
only memory) because the computer can only read information
from it; it can never write any new information on it. ROM isn’t
always hidden away on chips inside the computer’s chassis.
Many home video game machines and home computers use
removable ROM cartridges as permanent storage devices for
games and other programs.

21. Buses, Ports, and Peripherals
Information travels between a computer’s components
through groups of wires called buses. Buses typically
have 8, 16, or 32 wires; a bus with 16 wires is called a
16-bit bus because it can transmit 16 bits of information
at once—twice as many as an 8-bit bus.
Some buses connect to expansion slots inside the
computer’s housing. Users can customize their
computers by inserting special-purpose circuit boards
(usually called cards or just boards) into these slots.

22. Reading Tools
Optical-mark readers use reflected light to determine
the location of pencil marks on standardized test
answer sheets and similar forms.
• Bar-code readers use light to read universal product
codes (UPCs), inventory codes, and other codes
created out of patterns of variable-width bars.
• Magnetic-ink character readers read those odd-
shaped numbers printed with magnetic ink on checks.
• In many stores bar-code readers are attached to
point-of-sale (POS) terminals. These terminals send
information scanned by the wand to a mainframe
computer.

23. Digitizing the Real World
A scanner is an input device that can make a digital representation of
any printed image.
• A digital camera can be used to capture snapshots of the real world
as digital images.
• Audio digitizers contain circuitry to digitize sounds from microphones
and other audio devices.
• A video digitizer is a collection of circuits that can capture input from
a video source and convert it to a digital signal that can be stored in
memory and displayed on computer screens.
Sensing devices designed to monitor temperature, humidity, pressure,
and other physical quantities provide data used in robotics,
environmental climate control, weather forecasting, medical monitoring,
biofeedback, scientific research, and hundreds of other applications.

24. STORAGE DEVICES: INPUT MEETS OUTPUT
Tape drives are common storage devices on most mainframe computers and
some personal computers. The reason for the widespread use of magnetic
tape as a storage medium is because a typical magnetic tape can store
massive amounts of information in a small space at a relatively low cost.
Magnetic tape has one clear limitation: Tape is a sequential access medium.
Because retrieving information from the middle of a tape is time-consuming,
magnetic tape is used today mostly for backup of data and a few other
operations that aren’t time sensitive.

25. Magnetic Disks
The magnetic disk is a readily available alternative to tape as a storage
medium: A computer’s disk drive can rapidly retrieve information from
any part of a magnetic disk without regard to the order 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 transfer information
between machines and for packaging commercial software.
A hard disk is a rigid, magnetically sensitive disk that spins rapidly and
continuously inside the computer chassis or in a separate box connected
to the computer housing; the user never removes this type of hard disk.
There are several choices of removable media to fill the gap between
low-capacity, slow diskettes and nonremovable, fast hard drives:

26. Optical Disks
For multimedia applications, optical disks provide a storage alternative
to hard disks.
An optical disk drive uses laser beams rather than magnets to read and
write bits of information on the disk surface. While they currently aren’t as
fast as hard disks, optical disks have considerably more room for storing
data.
CD-ROM (compact disc—read-only memory) drives are optical drives
capable of reading CD-ROMs—data disks that are physically identical to
musical compact discs. Because CD-ROMs are read-only devices, they
can’t 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) will probably replace CD-ROMs for
multimedia applications because of their enormous capacity.

27. Solid-State Storage Devices
Flash memory is a type of erasable memory chip that
can serve as a reliable, low-energy, quiet, compact
alternative to disk storage. Most experts believe that
solid state storage technology like flash memory will
eventually replace disk and tape storage.

28. END OF CH04