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Chapter 5
Lecture Outline
Section 5.1
Microchips, Miniaturization, & Mobility
From Vacuum Tubes to Transistors to Microchips
The ENIAC was the last computer to use vacuum tubes, in 1946. The
ENIAC employed 18,000 vacuum tubes; unfortunately, a tube failure
occurred every 7 minutes and it took more than 15 minutes to find and
replace the faulty tube.
A transistor is essentially a tiny electrically operated switch that can
alternate between “on” and “off” many millions of times per second. The
first transistors were one-hundredth the size of a vacuum tube, needed
no warm-up time, consumed less energy, and were faster and more
reliable.
Transistors
marked
the
beginning
of
a
process
of
miniaturization that has not ended yet. Today more than 3 million
transistors can be squeezed into a half centimeter.
Today, transistors are part of an integrated circuit—an entire
electronic circuit, including wires, formed on a single “chip,” or piece, of
special material, usually silicon. An integrated circuit embodies what is
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called solid-state technology. Solid state means that the electrons are
traveling through solid material—in this case, silicon.
Silicon is an element that is widely found in clay and sand. It is used
not only because its abundance makes it cheap but also because it is a
semiconductor.
A
semiconductor
is
material
whose
electrical
properties are intermediate between a good conductor of electricity and
a nonconductor of electricity.
A chip, or microchip, is a tiny piece of silicon that contains millions of
microminiature electronic circuit components, mainly transistors.
Miniaturization Miracles: Microchips, Microprocessors, &
Micromachines
Microchips—“industrial
rice,”
as
the
Japanese
call
them—are
responsible for the miniaturization that has revolutionized consumer
electronics, computers, and communications. They store and process
data in all the electronic gadgetry we’ve become accustomed to.
There are different kinds of microchips: microprocessor, memory, logic,
communications, graphics and math coprocessor chips. Perhaps the
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most important is the microprocessor chip. A microprocessor
(“microscopic processor” or “processor on a chip”) is the miniaturized
circuitry of a computer processor—the part that processes, or
manipulates, data into information. When modified for use in machines
other than computers, microprocessors are called microcontrollers, or
embedded computers.
Mobility
In the 1980s portability, or mobility, meant trading off computing power
and convenience in return for smaller size and weight. Today, however,
we are getting close to the point where we do not have to give up
anything. Experts have predicted that small, powerful, wireless personal
electronic devices will transform our lives far more than the personal
computer has done so far.
Section 5.2
The System Unit
The Binary System: Using Two States
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Binary system has only two digits: 0 and 1. In the computer, the 0 can
be represented by the electrical current being off and the 1 by the
current being on. All data and programs that are used by a computer
are represented in terms of these binary numbers.
Capacity is denoted by any of the following:

Bit: In the binary system, each 0 or 1 is called a bit, which is short
for “binary digit.”

Byte: A group of eight bits is called a byte, and a byte represents
one character, digit, or other value.

Kilobyte: A kilobyte (K, KB) is about 1000 bytes. (Actually, it’s
precisely 1024 bytes, but the figure is commonly rounded.) The
kilobyte was a common unit of measure for memory or secondarystorage capacity in older computers.

Megabyte: A megabyte (M, MB) is about 1 million bytes (1,048,576
bytes). Most measures of microcomputer primary storage capacity
today are expressed in megabytes.
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
Gigabyte:
A
gigabyte
©2003 The McGraw-Hill Companies
(G,
GB)
is
about
1
billion
bytes
(1,073,741,824 bytes). This measure was formerly used with “big
iron” types of computers, but now is typical of secondary storage
(hard disk) capacity of today’s microcomputers.

Terabyte: A terabyte (T, TB) represents about 1 trillion bytes
(1,009,511,627,776 bytes).

Petabyte: A petabyte (P, PB) represents about 1 quadrillion bytes
(1,048,576 gigabytes).

ASCII: Pronounced “askey,” ASCII stands for American Standard
Code for Information Interchange and is the binary code most widely
used with microcomputers.

EBCDIC: Extended Binary Coded Decimal Interchange Code—is
used with large computers, such as mainframes.

Unicode uses two bytes (16 bits) for each character, rather than one
byte (8 bits). Instead of the 256 character combinations of ASCII-8,
Unicode can handle 65,536 character combinations, thus allowing
almost all the written languages of the world to be represented using
a single character set.
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The Parity Bit
Dust, electrical disturbance, weather conditions, and other factors can
cause interference in a circuit or communications line that is transmitting
a byte. A data error can be detected by using a parity bit. A parity bit,
also called a check bit, is an extra bit attached to the end of a byte for
purposes of checking for accuracy. Parity schemes may be even parity
or odd parity.
Machine Language
Machine language is a binary-type programming language that the
computer can run directly. To most people, an instruction written in
machine language, consisting only of 0s and 1s, is incomprehensible.
To the computer, however, the 0s and 1s represent precise storage
locations and operations.
The Computer Case: Bays, Buttons, & Boards
The system unit houses the motherboard (including the processor chip
and memory chips), the power supply, and storage devices. In
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computer ads, the part of the system unit that is the empty box with just
the power supply is called the case or system cabinet.
A bay is a shelf or opening used for the installation of electronic
equipment, generally storage devices such as a hard drive or DVD
drive. A computer may come equipped with four or seven bays. A tower
is a cabinet that is tall, narrow, and deep.
Power Supply
The power supply is a device that converts AC current (electricity
available from a standard wall outlet) to DC current to run the computer.
Because electricity can generate a lot of heat, a fan inside the computer
keeps the power supply and other components from becoming too hot.
The three principal types of power protection devices are:

Surge protector: is a device that protects a computer from being
damaged by momentary surges (spikes) of high voltage.

Voltage regulator: is a device that protects a computer from being
damaged by insufficient power—“brownouts” or “sags” in voltage.
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UPS: (uninterruptable power supply) is a battery-operated device
that acts as a surge protector and provides a computer with
electricity if there is a power failure.
The Motherboard & Microprocessor Chip
The motherboard, or system board, is the main circuit board in the
system unit. The motherboard consists of a flat board that fills one side
of the case. It contains both soldered, nonremovable components and
sockets or slots for components that can be removed—microprocessor
chip, RAM chips, and various expansion cards.
Expansion is a way of increasing a computer’s capabilities by adding
hardware to perform tasks that are beyond the scope of the basic
system. For example, you might want to add video and sound cards.
Upgrading means changing to newer, usually more powerful or
sophisticated versions, such as more powerful microprocessors or more
memory chips.
CISC (complex instruction set computing) chips, which are used
mostly in PCs and in conventional mainframes, can support a large
number of instructions, but at relatively low processing speeds.
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RISC (reduced instruction set computing) chips, which are used
mostly in workstations, a great many seldom-used instructions are
eliminated. As a result, workstations can work up to 10 times faster then
most PCs.
Processing Speeds: From Megahertz to Picoseconds

For microcomputers—megahertz and gigaherz: Micro-computer
microprocessor speeds are usually expressed in megahertz (MHz),
millions of machine cycles per second, which is also the measure of
a microcomputer’s clock speed. A high-end microcomputer or
workstation might perform at 100 MIPS or more, a mainframe at
200–1200 MIPS.
The latest generation of processors operates in gigahertz (GHz)—a
billion cycles per second. Intel’s latest chip, the Pentium 4, operates
at 1.4 gigahertz.

For workstations, minicomputers, and mainframes—MIPS:
Processing speed can also be measured according to the number of
instructions processed per second that a computer can process,
which today is in the millions. MIPS is a measure of a computer’s
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processing speed; MIPS stands for millions of instructions per
second that the processor can perform.

For supercomputers—flops: The abbreviation flops stands for
floating-point operations per second, a floating-point operation being
a special kind of mathematical calculation. This measure is
expressed as megaflops (mflops, or millions of floating-point
operations per second), gigaflops (gflops, or billions), and teraflops
(tflops, or trillions).

For all computers—fractions of a second: Another way to
measure cycle times is in fractions of a second. A microcomputer
operates in microseconds, a supercomputer in nanoseconds or
picoseconds—thousands or millions of times faster.
How the Processor or CPU Works: Control Unit, ALU, & Registers
Word size: the number of bits that the processor may process at any
one time.
CPU (central processing unit) is the “brain” of the computer; it follows
the instructions of the software (program) to manipulate data into
information.
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How Memory Works: RAM, ROM, CMOS, & Flash
RAM chips—to temporarily store program instructions and
data: Primary storage is temporary or working storage and is often
called memory or main memory; secondary storage is relatively
permanent storage.
RAM (random access memory) chips are for primary storage;
they temporarily hold (1) software instructions and (2) data before
and after it is processed by the CPU. Because its contents are
temporary, RAM is said to be volatile—the contents are lost when
the power goes off or is turned off.
ROM chips—to store fixed start-up instructions: Unlike RAM, to
which data is constantly being added and removed, ROM (readonly memory) cannot be written on or erased by the computer user
without special equipment. ROM chips contain fixed start-up
instructors—programs that are built in at the factory—that are
necessary for basic computer operations.
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CMOS chips—to store flexible start-up instructions: CMOS
(complementary metal-oxide semiconductor) chips are powered
by a battery and thus don’t lose their contents when the power is
turned off.
Flash memory chips—to store flexible programs: Also a
nonvolatile form of memory, flash memory chips can be erased
and reprogrammed more than once, and do not require a battery.
How Cache Works: Level 1 (Internal) & Level 2 (External)
Cache temporarily stores instructions and data that the processor is
likely to use frequently. Thus, cache speeds up processing.
There are two kinds of cache—Level 1 and Level 2:

Level 1 (L1) cache—part of the microprocessor chip: Level 1
(L1) cache, also called internal cache, is built into the processor
chip. Its capacity is less than that of Level 2 cache, although it
operates faster.
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Level 2 (L2) cache—not part of the microprocessor chip: Level 2
(L2) cache, also called external cache, resides outside the processor
chip and consists of SRAM chips.
Other Methods of Speeding Up Processing:
Interleaving, Bursting &
Pipelining
Interleaving:
a
process
in
which
the
CPU
alternated
communciation between two or more memory banks.
Bursting: Provides the CPU with additional data from memory
based on the likelihood that it will be needed.
Pipelining: Divides a task into a series of stages with some of
the work completed at each stage.
Ports & Cables
Port: A connecting socket or jack on the outside of the system unit into
which are plugged different kinds of cables. A port allows you to plug in
a cable or connect a peripheral device, such as a monitor, printer, or
modem, so that it can communicate with the computer system.
Ports are of several types:
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Serial ports: for transmitting slow data over long distances: A
line connected to a serial port will send bits one after another, like
cars on a one-lane highway.

Parallel ports—for transmitting fast data over short distances:
A line connected to a parallel port allows 8 bits (1 byte) to be
transmitted simultaneously.

SCSI ports—for transmitting fast data to up to seven devices in
a daisy chain:
A SCSI (small computer system interface) port
allows data to be transmitted in a “daisy chain” to up to 7 devices at
speeds (32 bits at a time) higher than those possible with serial and
parallel ports.

USB ports—for transmitting data to up to 127 devices in a daisy
chain: A USB (universal serial bus) port can theoretically connect up
to 127 peripheral devices daisy-chained to one general-purpose
port.

Plug and Play, which allows peripheral devices and expansion
cards to be automatically configured while they are being installed.
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Dedicated ports—for keyboard, mouse, phone, and so on: The
back of a computer also has other, dedicated ports—ports for
special purposes. Among these are the round ports for connecting
the keyboard and the mouse. There are also jacks for speakers and
microphones and modem-to-telephone jacks. Finally, there is one
connector that is not a port at all—the power plug socket, into which
you insert the power cord that brings electricity from a wall plug.

Infrared ports—for cableless connections over a few feet: An
infrared port allows a computer to make a cableless connection with
infrared-capable devices.
Expandability: Buses & Cards
Expansion slots are sockets on the motherboard into which you can
plug expansion cards.
Expansion cards—also known as expansion boards, adapter cards,
interface cards, plug-in boards, controller cards, add-ins, or add-ons—
are circuit boards that provide more memory or that control peripheral
devices.
The following are all types of expansion cards:
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
Graphics cards—for monitors

Sound cards—for speakers and audio output

Modem cards—for remote communication via phone lines

Network interface cards—for remote communication via cable

PC Cards—for laptop computers
Section 5.3
Secondary Storage
Floppy Disks
Floppy disk, often called a diskette or simply a disk, is a removable flat
piece of mylar plastic packaged in a 3.5-inch plastic case.

3.5-inch floppy disks—1.44 megabytes

Zip disks—100 megabytes

SuperDisks—120 megabytes

HiFD disks—200 megabytes
Hard Disks
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Hard disks are thin but rigid metal platters covered with a substance
that allows data to be held in the form of magnetized spots.
A head crash happens when the surface of the read/write head or
particles on its surface come into contact with the surface of the harddisk platter, causing the loss of some or all of the data on the disk.
There are two types of hard disks—nonremovable and removable.
Hard-Disk Technology for Large Computer Systems
Three types of secondary-storage devices are available for large
computers:

Removable packs: A removable-pack hard-disk system contains
6–20 hard disks, of 10.5- or 14-inch diameter, aligned one above the
other in a sealed unit. Capacity varies; some packs range into the
terabytes.

Fixed-disk drives: Fixed-disk drives are high-speed, high-capacity
disk drives that are housed (sealed) in their own cabinets.
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RAID storage system: A RAID (redundant array of inexpensive
disks) storage system, which consists of two or more disk drives
within a single cabinet or connected along a SCSI chain, sends data
to the computer along several parallel paths simultaneously.
Optical Disks: CDs & DVDs
An optical disk is a removable disk, usually 4.75 inches in diameter
and less than one-twentieth of an inch thick, on which data is written
and read through the use of laser beams. Some optical disks are used
strictly for digital data storage, but many are used to distribute
multimedia programs that combine text, visuals, and sound.
Among the types of optical disks are the following:

CD-ROM—for reading only: CD-ROM (compact disk read-only
memory)

CD-R—for recording on once: CD-R (compact disk–recordable)
disks

CD-RW—for rewriting many times: A CD-RW (compact disk–
rewritable) disk

DVD-ROM—the versatile video disk: A DVD-ROM (digital versatile
disk or digital video disk, with read-only memory)
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Magnetic Tape
Magnetic tape is thin plastic tape coated with a substance that can be
magnetized. Data is represented by magnetized spots (representing 1s)
or nonmagnetized spots (representing 0s).
Smart Cards

Smart cards: A smart card looks like a credit card but contains a
microprocessor and memory chip. When inserted into a reader, it
transfers data to and from a central computer. Smart cards can be
used as telephone debit cards.

Optical cards: Optical cards are plastic, laser-recordable, wallettype cards used with an optical-card reader.
Flash Memory Cards
Flash memory cards, or flash RAM cards, consist of circuitry on creditcard-size cards that can be inserted into slots connecting to the
motherboard. Flash memory cards are not infallible. Their circuits wear
out after repeated use, limiting their lifespan. Still, unlike conventional
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computer memory (RAM or primary storage), flash memory is
nonvolatile.
Online Secondary Storage
If the network computer or thin-client computer actually becomes as
popular as its promoters hope, the Internet itself will become, in effect,
your hard disk. When you sign up with a service, you usually download
from a Web site free software that lets you upload whatever files you
wish to the company’s server. For security, you are given a password,
and the files are supposedly encrypted to guard against anyone giving
them an unwanted look.
Section 5.4
Future Developments in Processing & Storage
DSP Chips: Processors for the Post-PC Era
Digital signal processors (DSPs) are integrated circuits designed for
high-speed data manipulation and used in audio, communications, and
image manipulation. DSPs are designed to manipulate digital signals in
speech, music, and video.
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Nanotechnology
A nanometer is a billionth of a meter, which means we are operating at
the level of atoms and molecules.
Optical Computing
Tomorrow’s computer might be optical, or opto-electronic—using light,
not electricity. With optical technology, a machine using lasers, lenses,
and mirrors would represent the on/off codes of data with pulses of light.
DNA Computing
Potentially, biotechnology could be used to grow cultures of bacteria
that, when exposed to light, emit a small electrical charge, for example.
The properties of this “biochip” could be used to represent the on/off
digital signals used in computing.
Quantum Computing
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Sometimes called the “ultimate computer,” the quantum computer is
based on quantum mechanics, the theory of physics that explains the
erratic world of the atom. A quantum computer stores information by
using states of elementary particles. Scientists envision using the
energized and relaxed states of individual atoms to represent data.
Other Possibilities: Molecular & Dot Computers
In the molecular computer, the silicon transistor is replaced with a single
molecule. In the dot computer, the transistor is replaced by a single
electron. These two approaches face formidable technical problems,
such as mass-producing atomic wires and insulators. No viable
prototypes yet exist.
Future developments in secondary storage
Greater Secondary Storage: Higher-Density Disks
Higher densities allow disks to be packaged in smaller sizes. In 2000,
IBM tripled the capacity of its silver-dollar-size removable hard drive
from 340 megabytes to 1 gigabyte. The Microdrive, as it’s called, is
designed for digital cameras, MP3 players, and handheld PCs.
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Molecular Electronics: Storage at the Subatomic Level
Holograms as storage: A hologram is a three-dimensional picture
created by two lasers. Dark and light areas of the hologram in a crystal
could be used to code binary information. In the future, holograms could
replace not only hard-disk drives but also memory chips.
Molecular magnets as storage: Researchers have succeeded in
creating a microscopic magnet, one molecule in size, derived from a
special combination of materials (manganese, oxygen, carbon, and
hydrogen).
Subtomic lines as storage: Physicists at NEC in Tokyo used a tool
called a scanning tunneling microscope (STM)—to paint and erase tiny
lines roughly 20 atoms thick.
Bacteria as storage: Scientists have reported research involving use of
bacteria to store data in three dimensions.
The Age of “Storewidth”
The arrival of broadband communication is sure to exacerbate the
demand for storage, “with billions of bytes of digital video and graphical
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data begging for storage space,” suggests one account. Technology
guru George Gilder already has a name for the future kind of storage:
storewidth.
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