Introduction to Computer System

CHAPTER 1
INTRODUCTION TO
COMPUTER SYSTEM

• This chapter will cover the following topics:
– Computer Hardware and Information Technology
Infrastructure
• The Computer System
• How Computers Represent Data
• The CPU and Primary Storage
• Microprocessors and Processing Power
• Multiple Processors and Parallel Processing
– Storage Input, and Output Technology
• Secondary Storage Technology
• Input and Output Devices
– Categories of Computers and Computer Systems
– Computer Software
– Programming Languange

Computer Hardware and Information
Technology Infrastructure
• Components of IT infrastructure consist of
software, data, and networks – require
computer hardware for their storage or
operation.

The Computer System
• Computer system consists of (see Figure
0.1):
– central processing unit (CPU)
– primary storage
– secondary storage
– input devices
– output devices
• Communications devices.

Figure 0.1: Hardware Component
of Computer Systems
Communication
Devices
Secondary
Storage
- Magnetic disk
Central
Processing Unit
(CPU)
Primary Storage
Input Devices
- Keyboard
Output Devices
- Printers
Buses

The System Unit
• What are common components inside the
system unit?
 Memory
 Adapter cards
 Sound card
 Video card
 Ports
 Drive bays
 Power supply
power supply
ports
drive bays
processor
memory
sound card
video card
 Processor

The System Unit
• What is the
motherboard?
 Main circuit
board in system
unit
 Contains adapter
cards, processor
chips, and
memory chips
 Also called
system board

• The CPU
– manipulates raw data into more useful form
and controls the other parts of the computer
system.
• Primary storage
– temporarily stores data and program
instructions during processing.
• Secondary storage
– devices store data and programs when they
are not being used in processing.

• Input devices
– convert data and instructions into electronic
form for input into the computer.
• Output devices
– convert electronic data produced by the
computer system and display them in a form
that people can understand.
• Communication devices
– provide connections between the computer
and communications networks.

• Buses
– are circuitry paths for transmitting data and
signals among the parts of the computer
system.

How Computers Represent Data
• All symbols, pictures or words must be reduced
to a string of binary digits.
• A binary digit is called a bit and represents either
a 0 or a 1.
• These are the only digits in the binary or base 2,
number system used by computers.
• A string of eight bits used to store one number or
character in a computer system is called a byte
(see Figure 0.2).

One byte for character A 01000001
The computer representation in ASCII for the
name Alice is
01000001 A
01001100 L
01001001 I
01000011 C
01000101 E

• To represent the numbers 0 through 9 and
the letters a through z and A through Z,
computer designers have created coding
systems consisting of several hundred
standard codes.
• In one code, for instance, the binary
number 01000001 stands for the letter A.

• Two common coding systems are Extended
Binary Coded Decimal Interchange Code
(EBCDIC) and American Standard Code for
Information Interchange (ASCII). See Table 0.1.
• EBCDIC represents every number, alphabetic
character, or special character with eight bits,
used primarily in IBM and other mainframe
computers.
• ASCII was originally designed as a seven-bit
code, but most computers use eight-bit versions.

• ASCII is used in data transmission, PCs
and some larger computers.
• The computers store a picture by creating
a grid overlay of the picture.
• Each single point in this grid, or matrix is
called a pixel (picture element) and
consists of a number of bits.

Data Representation
• How is a letter converted to binary form
and back?
Step 1.
The user presses
the capital letter D
(shift+D key) on
the keyboard.
Step 2.
An electronic signal for the
capital letter D is sent to the
system unit.
Step 3.
The signal for the capital letter D
is converted to its ASCII binary
code (01000100) and is stored in
memory for processing.
Step 4.
After processing, the binary
code for the capital letter D is
converted to an image, and
displayed on the output device.

The CPU and Primary Storage
• The CPU is the part of the computer
system where the manipulation of
symbols, numbers, and letters occurs, and
it controls the other parts of the computer
system.
The CPU

Processor
Control
Unit
Arithmetic
Logic Unit (ALU)
Arithmetic
Logic Unit (ALU)
Processor
• What is the central processing unit
(CPU)?
Input
Devices
Storage
Devices
Output
Devices
 Interprets and carries
out basic instructions
that operate a computer
Memory
Data Information
Instructions
Data
Information
Instructions
Data
Information
Control
Unit
 Control unit directs and
coordinates operations in
computer
 Arithmetic logic unit
(ALU) performs
arithmetic, comparison,
and logical operations
 Also called the processor

Processor
Control Unit
Memory
ALU
Processor
• What is a machine cycle?
Step 1. Fetch
Obtain program instruction
or data item from memory
Step 2.
Decode
Translate
instruction into
commands
Step 4. Store
Write result to memory
Step 3. Execute
Carry out command
 Four operations of the CPU comprise a machine cycle

The CPU and Primary Storage
Control Bus
Address Bus
Data Bus
Central Processing Unit (CPU)
Arithmetic Logic Unit (ALU)
22 + 11 = 33
Control Unit
Primary Storage
I
8
# U

• Three kinds of busses linked between the CPU,
primary storage and the other devices in the
computer system:
– Data bus
• Pass information in bi-directional.
– Address bus
• Transmits signals for locating a given address in primary
storage, indicating where data should be placed.
– Control bus
• Transmits signal specifying whether to read or write data to
or from primary storage address, input device or output
device.

• The characteristics of the CPU and
primary storage are very important in
determining a computer’s speed and
capabilities

The Arithmetic-Logic Unit and
Control Unit
• An arithmetic logic unit (ALU) and
control unit is one of the core
components of all central processing units.
• The ALU performs the computer’s
principal logical and arithmetic operations.
• It adds, subtracts, multiples, and divides,
determining whether a number is positive,
negative, or zero.

• ALU must be able to determine when one
quantity is greater than or less than another and
when two quantities are equal.
• The control unit coordinates and controls the
other parts of the computer system.
• It reads a stored program, one instruction at a
time and directs other components of the
computer system to perform the program’s
required tasks.

Processor
• Which processor should you select?
 The faster the processor, the more expensive the computer
Celeron
Itanium or Xeon
Pentium family
1.3 GHz and up
3.0 GHz and up
2.4 GHz to 3.0 GHz
Up to 2.4 GHz
2.2 GHz and up
Intel Processor Desired Clock Speed

Primary Storage
• Primary storage is a category of computer storage,
often called main memory.
• Has three functions:
– Stores all or part of the program that is being executed.
– Stores the operating system programs that manage the
operation of the computer.
– Holds data that the program is using.
• Data and program are placed in primary storage before
processing, between processing steps and after
processing has ended prior to being returned to
secondary storage or released as output.

• Modern primary storage devices include:
– Random access memory (RAM)
• is used for short-term storage of data or program instructions.
RAM is volatile. Its contents will be lost when the computer’s
electric supply is disrupted by a power outage or when the
computer turned off.
– Read-only memory (ROM)
• can only be read from. It cannot be written to. ROM chips
come from the manufacturer with programs already burned
in, or stored. ROM is used in general-purpose computers to
store important or frequently used programs, such as
computing routine for calculating the square roots of
numbers.

Memory
• What is random access memory (RAM)?
The more RAM a
computer has, the
faster it responds
Also called
main memory
or primary
storage
Most RAM is
volatile, it is lost
when computer’s
power is
turned off
Memory chips that can be
read from and written
to by processor

Memory
•How do program instructions transfer in and out of
RAM? Step 1. When you start the computer, certain
operating system files are loaded into RAM from
the hard disk. The operating system displays the
user interface on the screen.
Operating system
instructions
Web browser
instructions
Word processing
program instructions
Operating system
interface
Web browser
window
Word processing
program window
RAM
RAM
Web browser program
instructions are
removed from RAM
Web browser
window is no longer
displayed on
desktop
Step 2. When you start a Web browser, the
program’s instructions are loaded into RAM from
the hard disk. The Web browser window is
displayed on the screen.
Step 3. When you start a word processing
program, the program’s instructions are loaded
into RAM from the hard disk. The word
processing program, along with the Web Browser
and certain operating system instructions are in
RAM. The word processing program window is
displayed on the screen.
Step 4. When you quit a program, such as the
Web browser, its program instructions are
removed from RAM. The Web browser is no
longer displayed on the screen.

Must be
re-energized
constantly
Do not have to
be re-energized
as often as
DRAM
Most
common
type
Faster and
more reliable
than DRAM
chips
Memory
• What are two basic types of RAM chips?
Static
RAM
(SRAM)
Dynamic
RAM
(DRAM)
• Newer Type: Magnetoresistive RAM
(MRAM)

Memory
• What is read-only memory (ROM)?
Memory chips that store
permanent data
and instructions
Nonvolatile memory, it is not
lost when computer’s
power is turned off
Three types:
Firmware—
Manufactured with
permanently written
data, instructions,
or information
EEPROM
(electrically
erasable programmable
read-only memory)—
Type of PROM
containing microcode
programmer
can erase
PROM
(programmable
read-only
memory)—
Blank ROM
chip onto which
a programmer
can write permanently

Storage, Input, and Output
Technology
• Storage, input and output devices are
called peripheral devices because they are
outside the main computer system unit.

Secondary Storage Technology
• Secondary storage is used for relatively
long term storage of data outside the
CPU.
• Secondary storage is nonvolatile and
retains data even when the computer is
turned off.
• The most technologies are magnetic
disk, optical disk and magnetic tape.

Storage
• What is storage?
– Holds data, instructions, and information for future use
 Storage medium is physical material used for storage
 Also called secondary
storage

Storage Medium
(floppy disks, Zip disks,
hard disks, CDs)
Storage
• How does volatility compare?
Nonvolatile
 Storage medium is nonvolatile—contents retained
when power is off
Contents
retained
Contents
available to user
Memory
(most RAM)
(chips on motherboard)
Screen Display
ON OFF
Volatile
Display
disappears
Data and
instructions
available to user
Display
appears
Data and
instructions erased
 Memory is volatile—holds data and instructions
temporarily

Optical Discs
• What is a CD-ROM?
 Compact disc read-only memory
 Cannot erase or modify contents
 Typically holds 650 MB to 1 GB
 Commonly used to distribute multimedia and complex software

Optical Discs
• What are CD-Rs and CD-RWs?
Must have
CD recorder
or CD-R drive
Cannot erase
disc’s contents
CD-R (compact disc-recordable)
—cdisc you can write on once
CD-RW (compact disc-rewritable)
—ceerasable disc you can write on
multiple times
Must have
CD-RW software
and CD-RW drive

Optical Discs
•What is a DVD-ROM (digital
versatile disc-ROM or digital
video disc-ROM)?
 High capacity disc capable of
storing 4.7 GB to 17 GB
 Must have DVD-ROM drive or
DVD player to read DVD-ROM
 Stores databases, music,
complex software, and movies

Input and Output Devices
• Input devices
– Input devices gather data and convert them into
electronic form for use by the computer.
– Keyboard
• The principal method of data entry for entering text and
numerical data into a computer
– Pointing Devices
• A computer mouse is handheld device with point-and-click
capabilities that is usually connected to the computer by a
cable.
• Touch screens allows users to enter limited amounts of data
by touching the surface of a sensitized video display monitor
with finger or a pointer.

• Source Data Automation
– Captures data in computer-readable form at the time
and place they are created.
– Optical Character Recognition (OCR) devices
translate specially designed mark, characters, and
codes into digital form.
– Magnetic ink character recognition (MICR)
technology is used primarily in check processing for
the banking industry, which the bottom of typical
check contains characters identifying the bank,
checking account, and check number that are
preprinted using a special magnetic ink.

– A MICR reader translates these characters into digital
form for the computer.
– Handwriting-recognition devices such as pen-based
tablets, notebooks, and notepad are promising new
input technologies.
– These pen-based input devices convert the motion
made by an electronic stylus pressing on a touch-
sensitive tablet screen into digital form.
– Digital scanners translate image such as pictures or
documents into digital form.
– Voice input devices convert spoken words into digital
form for processing by the computer.
– Sensors are devices collect data directly from the
environment for input into a computer system.

What Is Input?
• What is input?
 Input device is any hardware component that
allows users to enter data and instructions
 Data or instructions entered into memory of computer

What Is Input?
• What are the two types of
input?
 Unprocessed text,
numbers, images,
audio, and video
 Instructions
 Programs
 Commands
 User responses
 Data

The Keyboard
• How is the keyboard
divided?
 Typing area
 Numeric keypad
 Function keys, special
keys that issue
commands

Pointing Devices
• What is a mouse?
 Pointing device that fits under palm of hand
 Pointing device controls
movement of pointer, also
called mouse pointer
 Mechanical mouse
has rubber or metal
ball on underside
mouse buttons
wheel
button
mouse pad
ball

Other Pointing Devices
• What is a trackball?
 Stationary pointing device
with a ball on its top or side
 To move pointer, rotate ball
with thumb, fingers, or palm
of hand

•What are a touchpad and a
pointing stick?
 Touchpad is small, flat,
rectangular pointing device
sensitive to pressure and motion
 Pointing stick is pointing device
shaped like pencil eraser
positioned between keys on
keyboard

• What are a joystick and a
wheel?
 Joystick is vertical
lever mounted
on a base
 Wheel is
steering-wheel-type
input device
 Pedal simulates
car brakes and
accelerator

• What is a light pen?
 Handheld input device
that can detect light
 Press light pen against
screen surface and then
press button on pen

• What is a touch
screen?
 Touch areas of screen with
finger
 Often used with kiosks

Keyboard and Pointing Devices
• What is a stylus and a digital pen?
 Looks like a ballpoint pen, but uses pressure to write
text and draw lines
 Used with graphics tablets, flat electronic boards

Voice Input
• How does voice recognition work?
Step 2. An analog-to-digital converter (ADC) translates
sound waves into digital measurements computer can
process. Measurements include pitch, volume, silences, and
phonemes. Phonemes are sound units such as aw and guh.
10010111010110101100001101
Step 3. Software compares
spoken measurements with those
in its database to find a match or
list of possible matches.
Matches
Step 4. To narrow a list down, software presents user with
a list of choices or uses a natural language component to
predict most likely match. User may correct any selection
made by software.
Natural Language Engine
Step 1. A user dictates text into a microphone.

Voice Input
•What is a MIDI (musical instrument
digital interface)?
 External device, such as electronic piano
keyboard, to input music and sound
effects

Digital Cameras
• How does a digital camera work?
Step 1. Point to the image to
photograph and take picture.
Light passes into the lens of the
camera.
Step 2. Image is focused on a
chip called a charge-coupled
device (CCD).
Step 3. CCD generates an analog
signal that represents the image.
Step 4. Analog signal is converted
to digital signal by analog-to-
digital converter (ADC).
Step 5. Digital signal processor
(DSP) adjusts quality of image and
usually stores digital image on
miniature mobile storage media in
the camera.
Step 6. Images are transferred to a
computer’s hard disk by plugging one
end of the cable into a camera and the
other end into a computer; or images
are copied to hard disk from storage
media used in the camera.
Step 7. Using software
supplied with the
camera, images are
viewed on screen,
incorporated into
documents, edited, and
printed.

Digital Cameras
• What is resolution?
 Sharpness and clarity of image
 The higher the resolution, the better the image
quality, but the more expensive the camera
 Pixel (picture element)
is single point in
electronic image
 Greater the number of
pixels, the better the
image quality

Video Input
• What is video input?
 Process of entering full-motion images
into computer
 Video capture card is
adapter card that converts
analog video signal into
digital signal that
computer can use
 Digital video (DV)
camera records video as
digital signals

Video Input
• What are a PC video camera and a Web
cam?
 PC video camerac—cDV camera used to capture video
and still images, and to make
video telephone calls on Internet
 Also called PC camera
 Web camc—cvideo camera
whose output displays on
a Web page

Scanners and Reading Devices
• What is a scanner?
 Light-sensing device that
reads printed text and
graphics
 Used for image processing,
converting paper documents
into electronic images
Drum
Flatbed
Pen or
Handheld
Sheet-fed

• What is an optical reader?
 Optical character recognition
(OCR) reads characters in
OCR font
 Optical mark recognition
(OMR) reads hand-drawn pencil
marks, such as small circles
 Device that uses light source to read characters, marks,
and codes and then converts them into digital data

• What is a bar code reader?
 Uses laser beams to read bar codes

What is a magnetic-ink character recognition
(MICR) reader?
 Can read text printed with magnetized ink
 Banking industry almost exclusively uses MICR
for check processing

Biometric Input
• What is biometrics?
 Authenticates person’s identity
by verifying personal
characteristic
 Fingerprint scanner captures
curves and indentations of
fingerprint
 Hand geometry system measures
shape and size of person’s hand

Biometric Input
• What are examples of biometric technology?
 Voice verification system compares live
speech with stored voice pattern
 Signature verification system recognizes
shape of signature
 Iris recognition system reads
patterns in blood vessels in back
of eye
 Biometric data is sometimes stored
on smart card, which stores
personal data on microprocessor
embedded in card

• Output Devices
– Display data after they have been processed.
– Cathode Ray Tube (CRT)
• The most popular form of information output.
• It works much like a television picture tube, with an
electronic gun shooting a beam of electrons to
illuminate the pixels on the screen.
– Printers
• Produce a printed hard copy of information output.
• Include impact printers ( dot-matrix printer), and
non-impact printers (laser, inkjet, and thermal
transfer printers).

– Plotters
• To created high-quality graphics documents with
multicolored pens to draw computer output.
• Slower than printers but are useful for outputting
large-size charts, maps or drawing.
– Voice output devices
• Converts digital output data into intelligible speech.
– Speakers
• To deliver an audio output such as music, that is
connected to the computer.

What is Output?
• What is output?
p. 300 Fig. 6-1 Next
 Data that has been processed into a useful form,
 Output device is any hardware component that can convey
information to user

Display Devices
• What is a display
device?
p. 302
 Output device that visually conveys information
 Information on display device sometimes
called soft copy
 Monitor houses display device as separate
peripheral

Printers
• What is a printer?
 Output device that
produces text and
graphics on paper
 Result is hard copy, or
printout
 Two orientations: portrait
and landscape
portrait
landscape

Speakers and Headsets
• What is an audio output device?
 Computer component that produces music, speech, or
other sounds
 Speakers and headsets are common devices

Speakers and Headsets
• What is voice output?
 Computer talks to you through speakers on computer
 Internet telephony allows you to have conversation
over Web

Categories of Computers and
Computer Systems
• Computers are classified into two:
– A special-purpose computer
– A general-purpose computer
• Special-Purpose Computers
– Is a computer designed for a particular function,
executing the same stored set of instructions
whenever requested.
– For example
• microwave ovens
• washing machine
• medical diagnostic equipment

• General-Purpose Computers
– Is a computer that can be used for solving many
different types of problems.
– Available in many sizes and a wide range of
capabilities.
– Can be classified as follows:
• 1. Microcomputers
a. Laptop computers
b. Desktop computers
c. Workstations
• 2. Minicomputers
• 3. Mainframe computers
• 4. Supercomputers

Microcomputers
• Sometimes referred to as a personal computer (PC), is
one that can be placed on a desktop or carried from
room to room.
• The smallest microcomputers are known as laptop
computers or notebook computers.
• Desktop computers are compact microcomputer
systems that fit on a desk and are designed for use by
individuals.
• A workstation is the largest type of microcomputer and
is generally used in scientific and engineering
applications.

Minicomputers
• More powerful and more expensive than
microcomputers.
• Are smaller and cheaper compared to
mainframes.
• Also can be server, which is used for
managing internal company networks or Web
sites.
• Server computers are specifically optimized to
support a computer network enabling users to
share files, software, peripheral devices (such
as printers), or other network resources.

Mainframe Computer
• The largest computer, a powerhouse
with massive memory and e extremely
rapid processing power.
• It is used for very large business,
scientific or military application where a
computer must handle massive amounts
of data or many complicated processes.

Supercomputer
• Is highly sophisticated and powerful
computer that is used for tasks requiring
extremely rapid and complex calculations
with hundreds of thousands of variable
factors.
• Used in many areas of scientific
research, weather prediction, aircraft
design, nuclear weapon and so on.

Computer Software
• Application Software
– Refers to programs that are developed to
solve some specific problems.
– There are two types of application software:
– application program to solve special classes of
problems
– Application programs that you can write to solve your
own problems.
– Examples of application software:
– word processing
– database programs
– spreadsheets
– graphic programs

• System Software
– Refers to programs that make the computer
usable and accessible to the developers
and programmers of applications software.
– Examples of system software:
– Operating systems
– Language translator
– Linker
– Loader
– Preprocessors

Programming Languages
• Programming Language is an agreed upon
format of symbols that allow a programmer to
instruct a computer to perform certain
predefined tasks.
• Provide features to support the data
processing activities, which include declaring
variables, evaluating numeric expressions,
assigning values to variables, reading and
writing data to devices, looping and making
decisions.

• a. Machine Languages
– Is the natural language of a computer.
– Does not need to translate and is ready for immediate
execution.
– Machine language instruction is a binary string of 0s
and 1s.
• 010 1 1000 0001 0000 1100 0000 0001 0000
– Are machine-dependent - each computer type has its
own machine language.
– Programs written in machine languages are not
portable because programs written in for one type of
computer cannot be run on another type

• Assembly Languages
– Consists of English-like abbreviations.
– Easier to understand.
• L 1, GROSSPAY
• S 1, TAX
• ST 1, NETPAY
– Program written in assembly languages cannot be directly
processed by a computer.
– Must use language translators, called assemblers, to convert
them to machine code.
– Disadvantages:
• In general, each assembly language instruction corresponds to
one machine language instruction. Therefore, the programs
written in them are lengthy.
– Because of variations in assembly languages, programs
written using them are not portable.

• High-Level languages
– Instructions are quite English-like, and a single
instruction can be written to correspond to many
operations at the machine level.
– For example, the assembly language program can
be written in high-level languages as follows:
• Netpay = gross pay – tax
– Are easier to learn than machine or assembly
languages.
– Have to be converted to machine languages before
they can be executed using compilers, system
software that translates a source program into an
almost executable object program

• For example:
– COBOL – developed in the 1960s for business
transactions.
– FORTRAN – developed for mathematic calculations.
– Pascal - is a structured high-level language.
– C – is designed to support only procedure-oriented
programming. Popular language for developing
system applications such as operating system and
compilers.
– Java – is an object-oriented language.
– C++ - is extension of C programming language that
support object oriented programming and procedure-
oriented approach.

Introduction to Computer System

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