Chapter 3
Inside the Computer
LEARNING
OBJECTIVES
Once you have read and studied this chapter, you will have learned:
HOW DATA ARE STORED AND REPRESENTED IN A COMPUTER SYSTEM (Section 3.1)
THE FUNCTION OF AND RELATIONSHIPS BETWEEN THE INTERNAL COMPONENTS
OF A PERSONAL COMPUTER, INCLUDING THE MOTHERBOARD, PROCESSOR, RAM
AND OTHER MEMORIES, PORTS, BUSES, EXPANSION BOARDS AND PC CARDS.
(Section 3.2)
HOW TO DISTINGUISH PROCESSORS BY THEIR WORD SIZE, SPEED, AND MEMORY
CAPACITY (Section 3.3)
SEVERAL APPROACHES TO PROCESSOR DESIGN (Section 3.4)
OVERVIEW AND LECTURE OUTLINE
TEACHING OBJECTIVES
 To emphasize the basic functions of a computer system: input, output, storage, and
processing.
 To stress the differences between data and information.
 To show how data are stored and represented in a computer system.
 To show how the CPU and RAM translate and process human language.
 To show that the temporary storage of data in RAM (primary storage) during the
processing function is different from its permanent storage on an external, secondary
storage medium.
 To identify and define internal computer components and show how they work together in
the computer system.
 To distinguish processors by word size, speed, and memory capacity.
 To explain several approaches to processor design.
NOTE: Ask your students to collect and bring to class current newspaper, magazine, or Internet
computer hardware advertisements as you begin the Chapter 3 lecture. We have found these to be
extremely useful in helping students master hardware terminology and relate classroom
knowledge to the real world. Also, bring examples of computer hardware (circuit boards, CPUs,
RAM chips, expansion boards, motherboards, etc.) to class or bring a computer to class for
students to “dissect.” Hands-on experience is invaluable and will reinforce what students perceive
to be somewhat “dry” computer vocabulary. With a significant portion of your budget at stake,
you want to make informed decisions when purchasing PCs. To get what you want and need in a
PC, and to get the most for your money, you need to have an overall understanding of the
essential elements of a computer. If you understand these essential elements of a PC, you’ll be
able to make informed decisions when purchasing PCs.
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3.1 GOING DIGITAL
A computer can have seemingly limitless capabilities.
The computer deals with everything as electronic signals. Electronic signals come in two
flavors—analog and digital. Analog signals are continuous wave forms in which variations in
frequency and amplitude can be used to represent information. With digital signals, everything is
described in two states: the circuit as either on or off. Generally, the on state is expressed or
represented by the number 1 and the off state by the number 0. A by-product of the computer
revolution is a trend toward “going digital” whenever possible.
For example, the movement in the recording industry has been away from analog
recording on records and toward digital recording on CD. When CDs are duplicated, each is an
exact copy of the original.
So how do you go digital? You simply need to digitize your material. To digitize means to
convert data, analog signals, images, and so on into the discrete format that can be interpreted by
computers.
TEACHING TIP
 The term hybrid computer is a misnomer. A hybrid computer is actually a digital
computer that can accept both digital and analog I/O. Any digital computer can be made
into a hybrid computer by attaching analog-to-digital and digital-to-analog converters.
Hybrid computers are used primarily for process-control applications.
 This text is oriented to the digital computer. Some instructors like to mention the analog
computer and the hybrid computer. For all practical purposes, the analog computer has
been replaced by the digital computer and has become part of computer history.
BINARY DIGITS: 1 AND 0
The electronic nature of the computer makes it possible to combine the two digital states–on and
off–to represent letters, numbers, colors, sounds, images, shapes, and even odors. An “on” or
“off” electronic state is represented by a bit, short for binary digit. In the binary numbering
system (base 2), the on-bit is a 1 and the off-bit is a 0.
Physically, these states are achieved in a variety of ways.
 In RAM, the two electronic states often are represented by the presence or absence of an
electrical charge.
 In disk storage, the two states are made possible by the magnetic arrangement of the
surface coating on magnetic tapes and disks.
 In CDs and CD-ROMs, digital data are stored permanently as microscopic pits.
 In fiber optic cable, binary data flow through as pulses of light. Bits may be fine for
computers, but human beings are more comfortable with letters and decimal numbers.
We like to see colors and hear sounds. Therefore, the letters, decimal numbers, colors,
and sounds we input into a computer system while doing word processing, graphics, and
other applications must be translated into 1s and 0s for processing and storage. The
computer translates the bits back into letters, decimal numbers, colors, and sounds for
output on monitors, printers, speakers, and so on.
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TEACHING TIP
 To demonstrate the concept of a bit, turn the lights off and say, “Off-bit,” then turn on
the lights and say, “On-bit;” repeat the sequence to make the point.
 The holes in the scrolls used with old-time player pianos provide a good example of the
on/off principle. Each of the 88 keys on a player piano is assigned a column on the scroll.
Where there is a hole in the column, a note is played.
 Show your class one full page of a hexadecimal dump of primary storage.
ENCODING SYSTEMS: BITS AND BYTES
Computers have their own language, better suited to electronic communication. Bits are
combined according to an encoding system to represent letters (alpha characters), numbers
(numeric characters), and special characters collectively referred to as alphanumeric characters.
ASCII and ANSI
ASCII
 Stands for American Standard Code for Information Interchange-pronounced “AS-key.”
 Equates a unique series of 1s and 0s with a specific character. Figure 3.2 shows the
ASCII bit string of printable commonly used characters or bytes (pronounced “bite”).
 The 7-bit ASCII code can represent up to 128 (27) bytes.
 By adding an 8th bit, the ASCII PC byte can represent up to 128 (28) printable bytes. The
extra bit is needed to represent control characters (such as ringing a bell) or non-character
images to complement their hardware or software product.
ANSI
 Stands for American National Standards Institute-pronounced “AN-zee.”
 Is an 8-bit encoding system that enables the sharing of text between Windows
applications.
 The first 128 characters of ANSI and ASCII encoding are exactly the same.
 The remaining 128 ANSI characters customize the Windows environment.
TEACHING TIP
ASCII is introduced as the encoding system that makes the combination of bits understandable to
humans. Compare encoding systems to the more familiar Morse code, created in 1844 by Samuel
F. B. Morse. Groups of bits are combined to represent alphabetic or numeric (alphanumeric) and
other characters, so that humans are able to communicate with the computer. Part of the
processing function is that the computer translates the group of bits into a byte, which is further
translated for human consumption by the encoding system. When the user enters a character, the
process is reversed. ASCII is only one of several codes used by different types of computers; it is
the most common encoding system used by microcomputers. The emergence of Unicode as a
standard depends on hardware and software developers over the next few years.
TEACHING TIP
 Write the word BIT on the board, then just below each letter write its ASCII code in
binary. (100 0010, 100 1001, 101 0100.) Then below that, write each character’s decimal
equivalent (66, 73, 84); below that, write each character’s hex equivalent.
 The first widely used coding system was the Morse code. In 1844 Samuel F. B. Morse
tapped out his first telegraphic message: “What hath God wrought?”
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TEACHING TIP
Draw an analogy between the lengthening of telephone numbers and the lengthening of the byte
to help students appreciate the move from six- to eight-bit encoding systems. Our parents and
grandparents grew up with five-digit telephone numbers; now we need seven to encompass the
local calling area. Just as seven-digit numbers allowed the installation of more telephones, the
eight-bit encoding system provides for the storage of a greater variety of characters and special
symbols.
UNICODE
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Stands for UNIform CODE.
Developed by a consortium of computer industry companies, including IBM, Microsoft,
and Sun Microsystems.
Is a 16-bit encoding system.
Enables computers and applications to talk to one another more easily and will
accommodate most languages of the world.
Is being proposed as a global encoding standard.
Requires more memory than traditional 8-bit codes—a major roadblock to global
conversion.
HEXADECIMAL
Perhaps the biggest drawback to using the binary numbering system for computer operations is
that we occasionally must deal with long and confusing strings of 1s and 0s. To reduce the
confusion, the hexadecimal, or base-16, numbering is used as shorthand to display the binary
number contents of RAM and disk storage.
VOCABULARY 3.1
Analog – Continuous wave forms that can represent sound, temperature, and velocity.
Digital – Computer data, or anything that has been translated into discrete format (1s and 0s).
Digitize – Convert analog to digital format.
Bit – Short for binary digit, a unit of the binary numbering system (base 2), which represents
either 1 for on, or 0 for off.
Binary – Base 2 numbering system, 0 and 1.
ASCII (American Standard Code for Information Interchange) – A seven-bit encoding
system which translates seven binary digits into one character.
ANSI (American National Standards Institute) – An eight-bit encoding system used by
Windows applications.
Unicode – A 16-bit encoding system that will enable computers and applications to talk to one
another more easily.
Hexadecimal – A base-6 numbering system that is used as shorthand to display the binary
contents of RAM and disk storage.
ANSWERS TO SECTION SELF-CHECK QUESTIONS
3-1.1 Bit is the singular of byte. (T/F)
3-1.2 Data are stored permanently on magnetic storage devices, such as magnetic disk. (T/F)
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3-1.3 Binary data flow through fiber optic cable as pulses of light. (T/F)
3-1.4 The hexadecimal numbering system has 26 unique numbers. (T/F)
3-1.5 What are the two kinds of electronic signals? (a) analog and digital, (b) binary and octal,
(c) alpha and numeric, or (d) bit and byte
3-1.6 The base of the binary number system is: (a) 2, (b) 8, (c) 16, or (d) 32.
3-1.7 The combination of bits used to represent a character is called a: (a) bits on/off, (b) binary
config, (c) 0-1 string, or (d) byte.
3-1.8 The 16-bit encoding system is called: (a) Unicorn, (b) Unicode, (c) Hexacode, or (d) 10
plus 6 code.
3-1.9 How many ANSI bytes can be stored in a 32-bit word? (a) 2, (b) 4, (c) 6, or (d) 8
ANSWERS TO SECTION DISCUSSION AND PROBLEM SOLVING QUESTIONS
3-1.1 Generally, computers are digital and human beings are analog, so what we say, hear, and
see must be converted, or digitized, for processing on a computer. Speculate on how a
family photograph might be digitized for storage and processing on a computer system.
(Family photographs could be scanned and stored on magnetic disks, CD-ROM, etc.)
3-1.2 Create a five-bit encoding system to be used for storing uppercase alpha characters,
punctuation symbols, and the apostrophe. Discuss the advantages and disadvantages of
your encoding system in relation to the ASCII encoding system. (Students will answer with
a variety of alphabetic and numeric systems. The biggest advantage of the ASCII encoding
system is that it is accepted and used by most computers, therefore one computer can
communicate effectively with another computer.)
3-1.3 How many characters can be represented with a 12-bit encoding system? (2 12)
3-1.4 Write your first name as an ASCII bit configuration. (Answers will vary by student.)
3.2 THE PC SYSTEM UNIT
The processor, RAM, and a variety of other electronic components are housed in the system unit,
usually a metal and plastic upright box (the tower), or inside the laptop’s shell.
TEACHING TIP
 Describe a typical microcomputer system and discuss the functions of its various
components.
 Today’s consumer is faced with multiple computer and PC configuration options and an
unending list of brand names from which to assemble his or her “perfect” computer.
Encourage students to learn as much as they can about available components and the
many ways they can be combined into a computer that works for them.
 Stress the importance of compatibility among components, and the need for drivers
(special software) to control each new component.
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THE MOTHERBOARD
The motherboard, a single circuit board, provides the path through which the processor
communicates with memory components and peripheral devices. Think of the processor as the
PC’s brain and the motherboard as the PC’s central nervous system. The motherboard’s chipset is
its intelligence and it controls the flow of information between system components connected to
the board. In a personal computer, the following are attached to the motherboard:
 Microprocessor (main processor)
 Support electronic circuitry (for example, one chip handles input/output signals from the
peripheral devices)
 Memory chips (for example, RAM and other types of memory)
 Expansion boards (optional circuit boards, such as a fax/modem)
The various chips have standard-sized pin connectors that allow them to be attached to the
motherboard and, therefore, to a common electrical bus that enables data flow between the
various system components. In a computer, the bus stops are the control unit, the arithmetic and
logic unit, RAM and other types of internal memory, and the device controllers that control the
operation of the peripheral devices. Ultimately, the type of processor and the amount of RAM
placed on the motherboard define the PC’s speed and capacity.
THE MICROPROCESSOR
The processor component of personal computer systems is a microprocessor, or simply a small
processor. The microprocessor is literally a “computer on a chip.” The Intel “286” (Intel 80286),
“386,” and “486” processors took us into the 1990s followed by the Intel Pentium® and
Pentium® Pro series. Most new system units have an Intel Pentium® III, Celeron® or Itanium
processor inside. The more expensive Pentium II-based PCs offer the greatest performance
whereas the less expensive Celeron-based PCs offer good value with reduced performance.
TEACHING TIP
For many years, Intel dominated the 80x86 microprocessor market. In June of 1994, other
competitors, the most formidable of which was AMD, began to produce microprocessors that
offered performance capabilities superior to that of the Intel microprocessors. Thus began an
intense rivalry. AMD's Duron workhorse processor is going head-to-head with Intel's Celeron to
dominate the business and home computing front. Other AMD processors that are going head-tohead against Intel Pentium microprocessors are the AMD's Athlon, which is known for its
superior multimedia performance on high-end desktops and workstations; the AMD's K6®-III,
which gives home and business computer users superior processing capability, realistic 3-D
computing experiences, and features a TriLevel Cache design; and the AMD K6®-2, which
features the new 3DNow! technology to enhance users' 3-D multimedia experience.
TEACHING TIP
 There are about 100 companies that make microprocessor chips.
 The Image Bank, “The Computer on a Chip,” visually and verbally explains the design,
fabrication, testing, and packaging of a silicon chip. A brief discussion of this fascinating
process will help bring home the point that computing and storage capabilities can be
packaged on chips no larger than a fingernail.
 Silicon Valley, California, was the first major electronics center, but competition is
emerging throughout the country. Boston has become “Silicon Valley East.” Newcomers
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to the chip industry include the Research Triangle Park in North Carolina and the
Austin, Texas, area.
What is the best way to introduce a small chip to the public? At the 1976 National
Computer Convention in New York City, Data General chose the navel of a belly dancer.
TEACHING TIP
 A mainframe-based computer center occupying one floor of a corporate headquarters
building in 1971 would need 26 floors to meet the company’s current computing needs if
it continued to use 1971 hardware. The processing capability of the IBM System 370/138,
a mid-sized mainframe computer in its day (1970-1975), will now fit on a single 1/4 inch
chip! What will fit in that same 1/4 inch space 20 years from now?
 Scientists are attempting to produce wafer-sized superchips that will hold all the memory
and logic they need for a particular task. With the current technology, the equivalent of a
superchip consists of hundreds of chips connected together on circuit boards that would
take up many times the space of a superchip. Superchips are probably the next step in
microminiaturization.
TEACHING TIP
 Processor speed and complexity have increased dramatically over the last decade. One
of the major problems encountered with each generation of CPU improvements is
dealing with heat buildup within the CPU. Today’s silicon-based Pentium processors
generate more BTUs of heat than the human body. Add to this the heat generated by the
rest of the computer’s internal components along with the monitor, printer, and other
peripherals.
 The proliferation of PCs has resulted in many air-conditioned offices being 40 to 60
percent underpowered.
 Silicon, which comes from sand and rock, is one of the most plentiful substances on earth,
and it is neither a conductor nor a nonconductor (insulator) of electricity—it is both. It
can be a conductor, like copper, or an insulator, like rubber; thus the term
semiconductor. Chips, and RAM.
 A switch from silicon to diamond microprocessor chips, may hold the key to heat
management in the next generation of computers. Diamonds conduct heat better than
silicon or copper and would permit heat to dissipate more rapidly inside the computer’s
system unit.
TEACHING TIP
 Through flexible integrated circuitry, IBM has combined inorganic and organic
materials in such a way as to create flexible transistors.
 We will be able to imbed circuitry in pliable products, including clothing.
 We will be wearing our PCs in the not-so-distant future.
 The cost of production of these flexible transistors is expected to be considerably less
than the traditional fabrication process.
STUDENT INVOLVEMENT EXERCISE
Ask students to research differences and similarities between any PC-compatible computer and
any non-PC-compatible technology. For example, students could compare and contrast the
PowerPC and Pentium families of computers. Ask students to debate and defend their preferred
technology with classmates.
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The Processor
The processor runs the show and is the nucleus of any computer system. Regardless of the
complexity of a processor, sometimes called the central processing unit or CPU, it has only two
fundamental sections: the control unit and the arithmetic and logic unit. These units work
together with random-access memory (RAM) and other internal memories to make the
processor—and the computer system—go.
The Control Unit
Just as the processor, or CPU, is the nucleus of a computer system, the control unit is the nucleus
of the processor. It has three primary functions:
 To read and interpret program instructions
 To direct the operation of internal processor components
 To control the flow of programs and data in and out of RAM
During program execution, the first in a sequence of program instructions is moved from RAM to
the control unit, where it is decoded and interpreted by the decoder.
The processor contains high-speed working storage areas called registers that can store no more
than a few bytes (see Figure 3.7). One register, called the instruction register, contains the
instruction being executed. The program register contains the location in RAM of the next
instruction to be executed.
The Arithmetic And Logic Unit
The arithmetic and logic unit performs all computations and all logic operations. The results are
placed in a register called the accumulator. Examples of computations include the payroll
deduction for social security, the day-end inventory level, and the balance on a bank statement. A
logic operation compares two pieces of data, either alphabetic or numeric. Based on the result of
the comparison, the program “branches” to one of several alternative sets of program instructions.
RAM
RAM, a read-and-write memory, enables data to be both read and written to memory. RAM is
solid state; that is, it is electronic circuitry with no moving parts. Most new PCs are being
equipped with synchronous dynamic RAM (SDRAM). SDRAM is able to synchronize itself
with the processor, enabling data transfer at more than twice the speed of previous RAM
technologies. The newer Rambus DRAM (RDRAM) is more expensive and six times faster than
SDRAM. Look for RDRAM in an increasing percentage of PCs. Physically, memory chips are
installed on single in-line memory modules, or SIMMs, and on the newer dual in-line memory
modules, or DIMMs. SIMMS are less expensive but have only a 32-bit data path to the
processor, whereas DIMMs have a 64-bit data path. The faster RDRAM chips are installed on
rambus in-line memory modules (RIMMs). RAM is volatile memory. That is, when the
electrical current is turned off or interrupted, the data are lost. In contrast to permanent storage on
disk, RAM provides the processor only with temporary storage for programs and data. RAM is
essentially a high-speed holding area for data and programs. In fact, nothing really happens in a
computer system until the program instructions and data are moved from RAM to the processor.
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TEACHING TIP
The prices of RAM chips have declined an average of 20 percent per year over the last two
decades. During the same period their storage capacity has quadrupled every 3 1/2 years. A
program instruction or a piece of datum is stored in a specific RAM location called an address.
Addresses permit program instructions and data to be located, accessed, and processed. The
content of each address changes frequently as different programs are executed and new data are
processed.
Other High-Speed Memories
To achieve even faster transfer of instructions and data to the processor, computers are designed
with cache memory. Cache memory is used by computer designers to increase computer system
throughput. Throughput refers to the rate at which work can be performed by a computer
system.
TEACHING TIP
 High-speed cache memory was first installed in computers in 1968.
 About half of your students will buy a PC by the time they graduate from college. Point
out that they should inquire about the capacity of cache memory as well as that of RAM.
Cache has a tremendous impact on system throughput.
Like RAM, cache is a high-speed holding area for program instructions and data.
However, cache memory uses internal storage technologies that are much faster than
conventional RAM. The contents of ROM (rhymes with “mom”), a nonvolatile technology, are
“hard-wired” by the manufacturer and can be “read only.” A variation of ROM is programmable
read-only memory (PROM). PROM is ROM into which you, the user, can load read-only programs and data.
TEACHING TIP
 ROM programs, called firmware (hardwired logic), are often written in microcode.
 A ROM program causes the operating system to be loaded to RAM.
 Read-only memory is evolving so quickly that various types of ROM are taking on
proprietary names rather than generic names like PROM and EPROM. The important
point to get across to the student is that nonvolatile solid-state storage is playing an
increasing role in computer technology.
Flash memory is a type of PROM that can be altered easily by the user. Flash memory is a
feature of many new processors, I/O devices, and storage devices.
What Happens Inside: Unraveling The Mystery
BASIC is a popular programming language. In practice, both programs and data would be stored
in RAM, which usually has a minimum of 64 million storage locations.
The statement-by-statement walkthrough in Figure 3.7 illustrates generally what happens as each
BASIC instruction is executed. Logic operations are similar, with values being compared between
RAM locations, the accumulator, and the various registers.
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STUDENT INVOLVEMENT EXERCISE
Have students bring current computer advertisements to class. Use those ads as ‘study guides’
for class discussion. Suggested questions: What do you think the personal computer circa 2005
will look like? (2010?) (2015?) How fast will it process data? How large will its memory
capacity need to be? How much will it cost? Where will you buy it?
The Instruction Cycle
We communicate with computers by telling them what to do in their native tongue—the machine
language. As you might expect, machine language instructions are represented inside the
computer as strings of binary digits.
Instructions are executed within the framework of a machine cycle. The timed interval that
comprises the machine cycle is the total of the instruction time, or I-time, and the execution
time, or E-time.
TEACHING TIP
 Most general-purpose computers use scalar processing; that is, they perform one
instruction at a time.
 Some of the larger processors do vector processing. In vector processing the computer
performs an arithmetic operation on a sequence of numbers called a vector, which is
usually a row or column of numbers. Vector processing is especially effective for the
processor-intensive jobs.
PUTTING IT ALL TOGETHER
The motherboard must be linked to I/O, storage, and communication devices to receive data and
return the results of processing.
A Fleet Of Buses
The motherboard includes several empty expansion slots that provide direct connections to the
common electrical bus. These slots let you expand the capabilities of a basic PC by plugging in a
wide variety of special-function expansion boards, also called expansion cards. These are the
more popular types of buses for PC compatibles:
TEACHING TIP
The term “bus” is appropriate for this part of the computer. The bus in a computer can easily be
compared to a complex mass transit and highway system.
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ISA bus. The most common expansion bus is the ISA bus. It’s also the oldest and
slowest.
PCI local bus. Recent innovations in bus technology have resulted in linking expansion
boards directly to the system’s common bus, sometimes referred to as the local bus. The
PCI local bus improves performance for today’s high-speed peripherals. Motherboards
include both the popular ISA bus and the PCI local bus.
SCSI bus. The SCSI bus, or “scuzzy” bus, provides an alternative to the expansion bus.
Up to 15 SCSI peripheral devices can be daisy-chained to a SCSI interface expansion
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card via the SCSI port. That is, the devices are connected along a single cable, both
internal and external, with multiple SCSI connectors.
TEACHING TIP
 Most high-end peripheral devices use a SCSI interface. However, some high-end and
specialized devices use a specialized or proprietary interface adapter card.
 Point out that most SCSI cards supplied with SCSI peripherals are designed to only
handle one device and damage can result if the user attempts to daisy-chain two or more
SCSI devices to one of these cards.
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Universal Serial Bus. The Universal Serial Bus (USB) is a relatively new bus standard
that permits up to 127 peripheral devices to be connected to a USB port. The USB will
eliminate the hassle of installing expansion cards. PC peripheral devices are designed to
connect to the USB port on the motherboard. The USB hot plug feature allows peripheral
devices to be connected to or removed from the USB port while the PC is running. This is
especially helpful to gamers who like to switch game controllers when they begin a new
game.
1394 bus. The 1394 bus is a recent bus standard that supports data transfer rates of up to
400 Mbps, over 30 times raster than the USB bus. In the Apple world, this type of bus is
called FireWire.
AGP Bus. The AGP bus is a special-function bus designed to accommodate the
Ports
In a PC, external peripheral devices usually come with a cable and a multipin connector. The
socket, called a port, provides a direct link to the PC’s common electrical bus on the
motherboard.
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Serial ports. Serial ports allow the serial transmission of data, one bit at a time. The
standard for PC serial ports is the 9-pin or 25-pin RS-232C connector.
TEACHING TIP
Serial port
 Facilitates serial transmission
 An interface for low-speed peripherals
 RS-232C and nine-pin
Parallel port
 Facilitates parallel transmission
 An interface for high-speed peripherals
 RS-232C and Centronics
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Parallel ports. Parallel ports allow the parallel transmission of data; that is, several bits
are transmitted simultaneously. Parallel ports use the same 25-pin RS-232C connector or
the 36-pin Centronics connector.
SCSI port. The SCSI port provides a parallel interface that enables faster data transmission than serial and parallel ports. The typical off-the-shelf PC compatible may not
come with a SCSI controller, the add-on circuitry needed for a SCSI port.
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USB port. The USB port (Universal Serial Bus port) is the most recent innovation in
high-speed device interfaces. Dedicated keyboard and mouse ports have a round 5-pin
connector.
1394 port. The 1394 port is the newest and fastest port. The 1394 bus is used by may
people to connect an external hard drive, a device that demands very fast data transfer
rates.
Dedicated keyboard and mouse ports. These two ports have a round 5-pin connector.
IrDA port. The IrDA port, infrared port, transmits data via infrared light waves.
PC GROWTH: ADDING CAPABILITIES
Today’s PCs are designed such that they can grow with your personal computing needs.
Expansion: Boards
The expansion slots associated with expansion buses (ISA) and local buses (PCI), and the SCSI
adapter let you add features to your PC by adding expansion boards. You will find these on most
PCs:
 Graphics adapter. The VGA (video graphics array) board and the newer AGP
(accelerated graphics port) board enable the interfacing of high-resolution monitors
with the processor.
 Sound. The typical sound card will have receptacles for a microphone, a headset, an
audio output, and a joystick.
 Data/voice/fax modem. A modem permits communication with remote computers via a
telephone-line link. The data/voice/fax modem performs the same function as a regular
modem, plus it has an added capability. It enables you to receive and make telephone
calls and it enables your PC to emulate a fax machine. A different type of modem, the
cable modem, is connected to the TV cable. Depending on your applications needs, you
might wish to enhance your system with some of these expansion boards:
 USB hub
 Network interface card
 SCSI interface card
 Video capture card
TEACHING TIP
The versatility of a PC depends largely on the number and types of expansion slots it has
available. This is an important item to check when buying a new computer. It’s very frustrating to
bring home a new peripheral device and discover you don’t have an empty expansion slot
available for it.
Pc Cards: Pcmcia Technology
The PCMCIA card, sometimes called a PC card, is a credit-card-sized removable expansion
module that is plugged into an external PCMCIA expansion slot. For example, one PC card
comes in the form of a mobile GPS (global positioning system). The mobile GPA card can be
used to pinpoint the latitude and longitude of the user within a few feet, anywhere on or near
earth.
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TEACHING TIP
PCMCIA technology is not really as standardized as it may appear. There are actually three
different sizes of PCMCIA slots in use today in portable computers. Look carefully before you
purchase a PC card or a portable PC.
TEACHING TIP
The U.S. Department of Defense owns the 24 satellites that make up the Global Positioning
System (GPS). Anyone with a ground receiver may determine his geographic location accurately
(within 10 to 100 meters) using this system. GPS systems are used by geologists to track the
activity of volcanoes, by outdoor sports enthusiasts to track their location while at sea, in the air,
or on the ground, and by drivers of automobiles to track the fastest route and keep abreast of
weather changes.
VOCABULARY 3.2
Motherboard – Circuit board on which electronic circuitry, microprocessor, and memory chips
are installed.
Chipset – A motherboard’s intelligence that controls the flow of information between system
components connected to the board.
Bus – Path over which signals flow to carry instructions among the control unit, arithmetic and
logic unit, and internal memory.
Device controllers – Microprocessors that control the operation of peripheral devices.
Pentium® – Family of microprocessors designed to better accommodate multimedia
applications.
Pentium PRO® – An Intel microprocessor that is more advanced than the Pentium
microprocessor.
Pentium II® – An Intel microprocessor that is more advanced and faster than its predecessors,
the Pentium and Pentium Pro microprocessors.
Pentium III® – Successor to the Intel® Pentium II microprocessor.
Celeron® – A line of Intel® microprocessors designed for low-cost PCs.
Itanium – Intel’s more expensive chip which offers the greatest performance.
Central processing unit or CPU – The logical component of a computer system that interprets
and executes program instructions.
Control unit – Reads and interprets program instructions, directs operation of processor, controls
data flow in and out of RAM.
Decoder – That portion of a processor’s control unit that interprets instructions.
Registers – High-speed temporary storage used by the control unit to handle instructions and data
during the processing function.
Instruction register – The register that contains the instruction being executed.
Program register – The register that contains the address of the next instruction to be executed
Arithmetic and logic unit – This performs all computations (addition, subtraction, multiplication
and division) and all logic operations (comparisons).
Accumulator – The computer register in which the result of an arithmetic or logic operation is
formed. (Related to arithmetic and logic unit.)
Synchronous Dynamic RAM (SDRAM) – RAM that is able to synchronize itself with the
processor enabling high-speed transfer of data (600 MHz) to/from the processor.
Rambus DRAM (RDRAM)—New RAM technology capable of very high-speed transfer of data
(600 MHz) to/from the processor.
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Single In-line Memory Modules (SIMMs) – Circuit boards on which RAM chips are stored.
Dual In-line Memory Modules, or DIMMs – Small circuit board, capable of holding several
memory chips, that has a 64-bit data path and can be easily connected to a PC’s system board.
(Contrast with SIMM).
Rambus In-line Memory Modules (RIMMs) – Small circuit boards capable of holding the
fastest RDRAM chips.
Volatile memory – Unstable, data are lost when electrical current is turned off.
Address – Specific RAM location.
Cache memory – High-speed holding area for programs and data which increases throughput.
Throughput – The time in which work can be performed by a computer system.
ROM – The contents of this memory are “hardwired” (designed into the logic of the memory
chip) by the manufacturer and can be “read only.”
Programmable read only memory (PROM) – Memory into which the user can load “readonly” programs and data.
Flash memory – Nonvolatile memory which can be altered by the user when necessary.
Nonvolatile memory – Solid-state RAM that retains its contents after an electrical interruption.
(Contrast with volatile memory.)
Machine language – Strings of binary digits (up to 64) that designate the address affected by the
operation.
Instruction cycle – The cycle of operations which the computer uses to process data, its speed is
determined by combining the instruction time (I-time) and the execution time (E-time).
Pipelining – Modern processors can begin executing another instruction before the current
instruction is completed.
Expansion slot – Receptacle into which optional components can be installed.
Expansion boards or cards – Allow the connection of a wide variety of peripheral devices to
computers with open architecture.
ISA bus – An expansion bus for PC compatibles.
PCI local bus (Peripheral Component Interconnect) – Developed by Intel, it assists in
regulating the variety of data transfer rates to some high-speed peripheral devices.
Small Computer System Interface (SCSI) bus – Allows the attachment of several, specially
designed peripheral devices to one port, through a daisy-chain effect.
Universal Serial Bus (USB) – Bus standard that permits up to 127 peripheral devices to be
connected to an external bus.
Hot plug – Universal serial bus (USB) feature that allows peripheral devices to be connected to
or removed from the USB port while the PC is running.
1394 bus – A recent bus standard that supports data transfer rates of up to 400 Mbps, over 30
times faster than the USB port.
FireWire – The Apple version of the 1394 bus.
AGP bus – A special-function bus designed to accommodate the throughput demands of highresolution 3-D graphics.
Serial port – Interface for peripheral devices which accept data transmission one bit at a time.
RS-232C connector – Standard 9-pin or 25-pin connector for micro serial ports.
Parallel port – Interface for peripheral devices which accept data transmission several bits at a
time.
Centronics connector – 36-pin connector used with parallel ports.
SCSI port – Device interface to which up to 15 peripheral devices can be daisy-chained to a
single USB port. (Contrast with USB port).
USB port – High-speed device interface to which up to 127 peripheral devices can be daisychained to a single USB port. (Contrast with SCSI port).
1394 port – The newest and fastest port used mainly to connect an external hard drive, a device
that demands very fast data transfer rates.
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IrDA port or infrared port – Enables wireless transmission of data via infrared light waves
between PCs, printers, and other devices (also called infrared port).
AGP (Accelerated Graphics Port) board – A graphics adapter that permits interfacing with
video monitors.
Modem – Permits communication with remote computers via a telephone-line link.
Data/voice/fax modem – A modem that permits data communication with remote computers via
a telephone-line link and enabling telephone calls and fax machine simulation via a PC.
Fax – A machine that transfers images of documents via telephone lines to another location.
Cable modem – Type of modem that is connected to the TV cable instead of telephone lines.
USB hub – Plug this device into a single USB port to expand the number of available ports
(usually to either three, four or five extra USB ports).
Network Interface Card (NIC) – This enables and controls the exchange of data between the
PCs in a local area network.
PC card or Personal Computer Memory Card International Association (PCMCIA) card –
Credit card-sized memory module or add-on board which increases the number of components in
smaller microcomputers, like notebook PCs.
GPS (Global Positioning System) – The mobile GPS can be used to pinpoint the latitude and
longitude of the user within a few feet, anywhere on or near earth.
ANSWERS TO SECTION SELF-CHECK QUESTIONS
3-2.1 The control unit is that part of the processor that reads and interprets program instructions.
(T/F)
3-2.2 The arithmetic and logic unit controls the flow of programs and data in and out of main
memory. (T/F)
3-2.3 PC cards can be hot swapped while the PC is running. (T/F)
3-2.4 The RS-232C connector provides the interface to a port. (T/F)
3-2.5 The 1394 bus transfers data at a slower rate than the USB bus. (T/F)
3-2.6 The rate at which work can be performed by a computer system is called: (a) system spray,
(b) throughput, (c) push through, or (d) volume load.
3-2.7 Which of the following memory groups are in order based on speed (slowest to fastest)? (a)
registers, cache, RAM, (b) cache, RAM, registers, (c) cache, registers, RAM, or (d) RAM,
cache, registers
3-2.8 The timed interval that comprises the machine cycle is the total of the instruction time and:
(a) execution time, (b) I-time, (c) X-time, or (d) delivery time.
3-2.9 Which one of the following would not be attached to a motherboard? (a) RAM, (b)
microprocessor, (c) FLOP, or (d) expansion board
3-2.10 Which port enables the parallel transmission of data within a computer system? (a) serial,
(b) parallel, (c) Centronics, or (d) speaker
3-2.11 PC components are linked via a common electrical: (a) train, (b) bus, (c) car, or (d) plane.
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3-2.12 Which two buses enable the daisy-chaining of peripheral devices? (a) USB and SCSI, (b)
SCSI and infrared, (c) USB and PCI local bus, or (d) PCI local bus and ISA
ANSWERS TO SECTION DISCUSSION AND PROBLEM SOLVING QUESTIONS
3-2.1 List at least 10 products that are smaller than a toaster oven and use microprocessors. Select
one and describe the function of its microprocessor. (watch, camera, VCR, Nintendo/Sega,
many toys like talking stuffed animals, CD player, etc.)
3-2.2 Describe the advantages of a USB port over a parallel port. Also, describe the advantages of
a parallel port over a serial port. (USB supports up to 125 devices with hot swap
technology. Parallel port for faster throughput.)
3-2.3 Distinguish between RAM and flash memory. Be specific. (RAM is volatile and flash is
nonvolatile memory.)
3-2.4 Which two functions does the arithmetic and logic unit perform? Give a real-life example
for each function. (For example, arithmetic function (Quantity of apples purchased x price
per pound = total price of apples purchased). For example, logic function (If birthdate is =
May 14, then "Happy Birthday," else enter a blank space.)
3-2.5 Explain the relationship between a microprocessor, a motherboard, and a PC. (The PC
contains the motherboard which contains the circuitry to connect the microprocessor to all
other components of the computer system.)
3-2.6 Generally describe the interaction between the processor’s control unit, registers, and RAM.
(The control unit directs the input and output of data and instructions to the registers in the
CPU.)
3-2.7 Give one example of where each of these memory technologies might be used in a personal
computer system. (Answers will vary by student.)
3-2.8 Illustrate the interaction between the user RAM and the accumulator in the arithmetic and
logic unit for the following basic program. Use the model shown in Figure 3.7.
INPUT “Enter ages for 3 children”; A, B, C
LET AVGAGE=(A+B+C)/3
PRINT “The average age is”; AVGAGE
END
(The user inputs the three ages which are stored in RAM. The control unit then sends each
age to the accumulator where they are added together and then averaged and sent back to
RAM for output to the user.)
3-2.9 List three expansion boards you would like to have on your own PC. How would you use
these added capabilities? (Answers may include sound blaster card (for higher quality
sound), fax/modem card (to add fax/modem capability), graphics adapter card (for higher
graphics resolution).)
3-2.10 Describe a hot swap as it relates to a PCMCIA-compliant interface. (Cards can be
removed and replaced without turning the computer off.)
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3-2.11 Why do you suppose PC motherboards are designed to accommodate several types of
buses? (Because different buses support different computer operations (ex. USB bus is
entirely different than a PCMCIA bus.)
3.3 DESCRIBING THE PROCESSOR
When describing computers or processors, we talk about word size, processor speed and
the memory capacity.
TEACHING TIP
This topic builds on concepts from topic 3-2 which describe the processor, and shows how to
differentiate among the many types of processors available, including by word length, processor
speeds, and RAM capacity. When describing computers or processors, we talk about word size,
speed, and the memory capacity.
WORD SIZE
A word describes the number of bits that are handled as a unit within a particular computer
system’s bus. Internal processing involves the movement of data and commands between
registers, the control unit, and the arithmetic and logic unit (see Figure 3.7). Many popular
computers have 64-bit internal processing but only a 32-bit path through the bus. The word size
for internal processing for most modern PCs is 64 bits (eight 8-bit bytes). Workstations,
mainframes, and supercomputers have 64-bit word sizes and up.
TEACHING TIP
Word lengths vary depending on the computer, and also may vary within one computer,
depending on whether data or programs are being processed. A Pentium works with 64-bit
words.
TEACHING TIP
A few inches of flat 16- and 32-wire cable makes an excellent demonstration of the concept of a
word.
PROCESSOR SPEED
A tractor can go 22 miles per hour (mph), a minivan can go 90 mph, and a slingshot drag
racer can go 300 mph. These speeds, however, provide little insight into the relative capabilities
of these vehicles. What good is a 300-mph tractor or a 22-mph minivan? Similarly, you have to
place the speed of computers within the context of their design and application. Generally, PCs
are measured in MHz, workstations and mainframes are measured in MIPS, and supercomputers
are measured in FLOPS.

Megahertz: MHz. The PC's heart is its crystal oscillator and its heartbeat is the clock
cycle. The crystal oscillator paces the execution of instructions within the processor. A
micro's processor speed is rated by its frequency of oscillation, or the number of clock
cycles per second. Most modern personal computers are rated between 400 megahertz, or
MHz (millions of clock cycles) to 1 Gigahertz, or GHz (billions of clock cycles). The
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elapsed time for one clock cycle is 1 divided by the frequency. For example, the time it
takes to complete one cycle on an 800-MHz processor is 1/800,000,000, or
0.00000000125 seconds, or 1.25 nanoseconds (1.25 billionths of a second). Normally
several clock cycles are required to fetch, decode, and execute a single program
instruction. The shorter the clock cycle, the faster the processor.
TEACHING TIP
The original 25 MHz Intel 80486 microprocessor was two to five times faster than the 33-MHz
Intel 80386, primarily because of system integration and the compactness of its components.
High-end Pentium or Itanium microprocessors will operate in the 800 MHz to 1 plus GHz range.

MIPS. Processing speed may also be measured in MIPS, or millions of instructions per
second.

FLOPS. Supercomputer speed is measured in FLOPS—floating point operations per
second. State-of-the-art supercomputers operate at speeds in excess of a trillion FLOPS.
TEACHING TIP
Chip wars continue as major processor manufacturers AMD and Intel continue to leapfrog one
another to be the maker of the fastest processor. In December 1999, AMD introduced a 750 MHz
chip. Now Intel has an 800 MHz Pentium III chip. Both companies are working feverishly toward
a 1000 MHz chip in the near future. Computers are rated between 400 and 900 megahertz, or
MHz, and 1 plus GHz.
MEMORY CAPACITY
Memory capacity for most computers is stated in terms of megabytes (MB). High-speed
cache memory capacities usually are measured in kilobytes (KB), the most common being 512
KB of cache.
Some high-end mainframes and supercomputers have more than 8000 MB of RAM. Their RAM
capacities are stated as gigabytes (GB). It’s only a matter of time before we state RAM in terms
of terabytes (TB). Occasionally you will see memory capacities of individual chips stated in
terms of kilobits (Kb) and megabits (Mb).
TEACHING TIP
To give your students some idea of the practical meaning of capacity, the King James Version of
the Holy Bible contains 4.5 million characters (about 4.3MB).
TEACHING TIP
RAM Capacity History.
 Before 1988, KB
 1985-1992, 1 or 2MB
 1992-1994, rapid increase from 1MB to 16MB
 1995, with the emergence of Windows 95 and OS/2 Warp, minimum capacity jumped
from 4MB to 16MB.
 21st Century, 128MBA to 500 MBA for PCs.
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TEACHING TIP
Primary and secondary storage capacities are usually stated in terms of MB, but capacities of the
individual chips are stated in terms of bits. RAM can be expanded by adding expansion cards,
(SIMMs, DIMMs and RIMMs) that can include from 4-64 MB of RAM per card, depending on the
manufacturer and the machine. The price of this additional memory fluctuates with the market
availability of silica.
DIFFERENCES IN PROCESSOR PERSONALITY
Word size, speed, and memory capacity are the primary descriptors of processors.
However, computers, like people, have their own “personalities.” That is, two similarly
described computers might possess attributes that give one more capability than the
other. For example, one 64-bit, 500-MHz, 512-MB PC might have 1 MB of cache memory and
another only 512 KB. Remember this: When you buy a PC, the basic descriptors tell most but not
the entire story.
TEACHING TIP
Sometimes computer systems are categorized by how they are to be used, as opposed to their
capacity. For example, PCs are associated with personal applications, mainframes and server
computers with corporate-level processing, and supercomputers with processor-intensive
scientific applications.
VOCABULARY 3.3
Word – The number of bits that are handled as a unit within a computer’s bus or during
internal processing.
Megahertz (MHz) – Millions of clock cycles.
Gigahertz (GHz) – Billions of clock cycles.
Millions of instructions per second (MIPS) – Measures processing speed of workstations,
mainframes, and some high-end PCs.
Floating point operations per second (FLOPS) – Measures processing speed of
supercomputers.
Megabytes (MB) – 1,048,576 (2 20 ) bytes.
Kilobytes (KB) – 1024 (2 10) bytes.
Gigabytes (GB) – About one billion bytes.
Terabytes (TB) – About one trillion bytes.
Kilobits (Kb) and megabits (Mb) – Terms which refer to memory capacities of individual
chips.
ANSWERS TO SECTION SELF-CHECK QUESTIONS
3-3.1 The word size of all PCs is 32 bits. (T/F)
3-3.2 MIPS is an acronym for “millions of instructions per second.” (T/F)
3-3.3 A gigabyte of RAM has more storage capacity than a megabit of RAM. (T/F)
3-3.4 Which has the most bytes? (a) a kilobyte, (b) a gigabyte, (c) a megabyte, or (d) a big byte
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3-3.5 We describe computers in terms of what three characteristics? (a) speed, memory, and
word size, (b) word meaning, layer width, and memory, (c) memory, cache, and register
size, or (d) SDRAM, E-time, and bus length
3-3.6 The time it takes to complete one cycle on a 750-MHz processor is: (a) 1/750,000,000
seconds, (b) .000000075 seconds, (c) 7.5 microseconds, or (d) 7.5 thousandths of a second.
ANSWERS TO SECTION DISCUSSION AND PROBLEM SOLVING QUESTIONS
3-3.1 Assume a move data instruction requires five clock cycles. Compute the time it takes, in
nanoseconds, to execute a move data instruction on a 600-MHz processor. (12.5)
3-3.2 Convert 5 MB to KB, Mb, and Kb. Assume a byte contains eight bits. (5120 KB, 40 Mb,
40960 Kb)
3.4 PROCESSOR DESIGN
PARALLEL PROCESSING
The concept of using multiple processors in the same computer system is known as parallel
processing. In parallel processing, one main processor examines the programming problem and
determines what portions, if any, of the problem can be solved in pieces. Parallel processing on a
large scale is referred to as massively parallel processing. These super fast supercomputers have
sufficient computing capacity to attack applications that have been beyond that of computers with
traditional computer designs.
NEURAL NETWORKS
Scientists are studying the way the human brain works and are attempting to build computers that
mimic the incredible human mind. The base technology for these computers is neural networks.
The neural network computer employs hundreds, even thousands, of small, interconnected
processors, called processing units.
The primary difference between traditional digital computers and neural networks is that
digital computers process structured data sequentially whereas neural networks process
unstructured information simultaneously.
VOCABULARY 3.4
Parallel processing – Several processors work together to process pieces of data and
instructions, then reassemble them.
Massively parallel processing (MPP) – Parallel processing on a larger scale, using thousands
of integrated microprocessors within one supercomputer.
Neural networks – A field of artificial intelligence in which millions of chips (processing
elements) are interconnected to enable computers to imitate the way the human brain works.
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ANSWERS TO SECTION SELF-CHECK QUESTIONS
3-4.1 In parallel processing, two main processors examine the programming problem and
determine what portions, if any, of the problem can be solved in pieces. (T/F)
3-4.2 In a single processor environment, the processor addresses the programming problem
sequentially. (T/F)
3-4.3 Parallel processing on such a large scale is referred to as massively trapezoidal processing.
(T/F)
3-4.4 The concept of using multiple processors in the same computer system is known as: (a)
massive processing, (b) acute processing, (c) parallel processing, or (d) perpendicular
processing.
3-4.5 The base technology for computers that mimic the human mind is called: (a) HAL, (b)
neural network, (c) human brain focus, or (d) interconnected processing.
3-4.6 Neural networks process unstructured information: (a) intermittently, (b) sequentially, (c)
simultaneously, or (d) as time permits.
ANSWERS TO SECTION DISCUSSION AND PROBLEM SOLVING QUESTIONS
3-4.1 Describe the computer you use at home, at work, or in the PC laboratory. (Answers will
vary by student.)
3-4.2 Speculate on an application that might be appropriate for parallel processing and one that
might be appropriate for a neural network-based system. (Parallel processing may be useful
for breaking a large, mathematically-based problem down into smaller pieces. Each
processor would handle the computations for a different part of the problem. The main
processor would accumulate the end results from the individual processors and output a
final solution. Neural networks might one day be used to simulate human feeling and
restore usage to damaged or previously unusable limbs.)
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