Introduction to computer hardware

Introduction To Computer
K. A. M Lutfullah,PRINCE2, ITIL

Digital Computers
 The computers that we use are digital, not
analogue computers
 Analogue technology
– The signal is directly analogous to the information it
represents
– The signal is continuous and in direct proportion to the
source of the information
• In a thermometer, mercury rises in direct proportion to the
temperature
• In an amplifier or telephone, the electronic voltage signal
varies in direct proportion to the frequency and amplitude of
the sound waves it represents

Digital Technology
 Digital technology
– The signal is discrete
– The information is broken down into pieces, and each piece is
represented separately
– Analogue information is measured many times per second (the
sampling rate) and each measurement is represented as a number
– How music is stored on a compact disc - the disc stores numbers
representing specific voltage levels sampled at specific times
– Can be used to digitize sound, video, graphics, etc.
 Our computers work with digital technology, hence the
term digital computers

Storage of Programs and Data
 Sampling is only one way to digitize information
 Since our computers work ONLY with numbers,
everything (not just analogue information such as
sound and video) must be converted to numbers
– Text (letters and special characters) gets converted to
numbers (A = 65), using a standard coding convention
called ASCII
– Graphics (images), gets broken down into pieces
(pixels) and each colour gets a number

Binary Numbers
 But how do we store numbers in a computer?
– We could use the digits 0, 1, 2,….., 9 from the base 10
(decimal) numbering system that we are used to?
– We would need a unique physical representation in the
computer for each of the 10 digits, 0, 1, 2,……..,9

Binary Numbers
 Devices that store and move information are cheaper and more reliable
if they have to represent only two states
• A circuit conducts current (1) or does not (0)
• A position on a diskette is magnetized in one direction (1) or
the opposite direction (0)
• A position on a CD is pitted (1) or is not (0)
 Once information is digitized, it is represented and stored in memory
using the binary number system
 A single binary digit (0 or 1) is called a bit
 A single bit can represent two possible states, like a light bulb that is
either on (1) or off (0)
 Permutations of bits are used to store values. All information is
represented as combinations of the two digits 0 and 1.

Binary Numbers
1 bit
0
1
2 bits
00
01
10
11
3 bits
000
001
010
011
100
101
110
111
4 bits
0000
0001
0010
0011
0100
0101
0110
0111
1000
1001
1010
1011
1100
1101
1110
1111
 Each permutation can represent a particular item
 1 bit = 2 choices, a 0 or a 1
 8 bits = 1 byte = 256 different combinations of 0’s and 1’s
 There are 2
N
permutations of N bits
 Therefore, N bits are needed to represent 2
N
unique items

Binary Numbers
 So how do we convert decimal numbers to binary
numbers?
– i.e. if we enter the number 9 into the computer, how is it
changed to 1001 for computer storage and processing?
 Or when we want to display or output information
from the computer, how do we convert binary
numbers to decimal numbers?
 See the slides titled Number Systems in the
Additional Material at the end of this lecture

Hardware
 Units of measure
– All done relative to a Byte (8 bits - 1 character)
– KB = Kilobyte - 1 thousand bytes (1024)
– MB = Megabyte - 1 million bytes (1,048,576)
– GB = Gigabyte - 1 billion bytes
– TB = Terabyte - 1 trillion bytes
 To understand how data is represented and stored
on a diskette, see the slides titled Diskettes in the
Additional Material at the end of this lecture

Computer System
 Hardware - physical parts of the computer
 Software - instructions to the computer
 Data - raw facts the computer can manipulate
 People - also known as users

Computer System Flow
Input
Process
Output Storage
Communication
Central
Processing
Unit
Main
Memory
Floppy Disk
Hard Disk
Monitor
Keyboard

Computer Hardware
Computer consists of
 Central Processing Unit (CPU)
 Memory
 Input and Output Devices
 Storage Devices
 BUS
 Communication Devices
Output
Storage
Input
Processor
Input and
output
Memory

Computer Hardware
 Input Devices

Computer Hardware
 Output Devices

Computer Hardware
 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.

Computer Hardware
 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 0 or 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.

How Computers Represent Data (Contd…)
 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.

 How is a letter converted to binary form and back?

CPU
 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.
 Interprets and carries out basic instructions that operate a
computer
– Control unit directs and
coordinates operations in
computer
– Arithmetic logic unit (ALU)
performs arithmetic,
comparison, and logical
operations
 Also called the processor

CPU
 Computer chip: also called the
microprocessor may contain an
entire processing unit.
 Computer chips contain
millions of transistors. They
are small pieces of semi-
conducting material (silicon).
 An integrated circuit is
embedded in the silicon.
Computers are made of many
chips on a circuit board.

ALU
 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.

CPU
 What is a machine cycle?
– Four operations of the CPU comprise a machine cycle

CPU & Processor
– Processor speed: The speed at which a microprocessor
executes instructions. This is usually measured in
megahertz (MHz).
– Brands of Processors include:
• Pentium
• Celeron
• MAC
• AMD
• Cyrix

BUS
 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.

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.

How is memory measured?
 By number of bytes available for storage

 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)?

Memory
 How do program instructions transfer in and out of RAM?

Memory
 What are two basic types of RAM chips?
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
Static RAM (SRAM)
Dynamic RAM (DRAM)

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
 How does volatility compare?
– Storage medium is nonvolatile—contents retained when power is
off
– Memory is volatile—holds data and instructions temporarily
Storage Medium
(floppy disks, Zip disks,
hard disks, CDs)
Nonvolatile
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

Magnetic disk
 There are two kinds of magnetic disk:
– floppy disks
– hard disks
 Magnetic Disks permit direct access to individual
records so that data stored on the disk can be
directly accessed regardless of the order in which
the data were originally recorded.
 Disk storage is often referred to as a direct access
storage device (DASD).

Magnetic Disks
 What is a floppy disk?
– Portable, inexpensive storage
medium (also called diskette)
– Thin, circular, flexible disk
enclosed in rigid plastic shell
 What is a floppy disk
drive?
– Device that reads from and
writes to floppy disk
– Also called secondary storage
Thin, circular, flexible film enclosed
in 3.5” wide plastic shell
shutter
shell
liner
magnetic
coating
flexible thin film
metal hub
One floppy drive, named drive A

Magnetic Disks
 What is a hard disk?
– The hard-drive is a mechanical storage device typically
located internally.
• Magnetic. Fast recording and recovery of data
• Large storage capacity
• Primary storage device for data and programs
• Speed is measured in R.P.M.’s hard disk installed in system unit

Magnetic Disks
 What are tracks and sectors?
Track
is narrow
recording band
that forms full
circle on disk
Sector
stores up to
512 bytes
of data
Formatting prepares disk for use and marks bad sectors as unusable

Magnetic Disks
 How does a hard disk work?
Step 1.
Circuit board controls
movement of head actuator
and a small motor.
Step 2.
Small motor spins
platters while
computer is running.
Step 3.
When software requests a
disk access, read/write
heads determine current
or new location of data.
Step 4.
Head actuator positions
read/write head arms over
correct location on platters
to read or write data.

Optical Disk
 Also called compact disks or laser
optical disks, used laser technology
to store data at densities many times
greater than those of magnetic disks.
 The most common optical disk
system used with PCs called CD-
ROM (compact disk read only
memory).
 CD-ROM is read-only storage.
 What are optical discs?
– Flat, round, portable metal discs made
of metal, plastic, and lacquer
– Can be read only or read/write
– Most PCs include an optical disc drive
Push the same
button to close
the tray.
Insert the disc,
label side up.
Push the button to
slide out the tray.

Optical Discs (Contd…)
 How does a laser read data on an optical disc?

 How is data stored on an optical disc?
– Typically stored in single track
– Track divided into evenly sized sectors that store items
single track spirals
to edge of disc
disc sectors

 WORM (write once/read memory) or CD-R (compact
disk-recordable) optical disk systems allow users to record
data only once on an optical disk.
 New CD-RW (CD-Rewritable) technology has been
developed to allow users to create rewritable optical disks.
 Digital-video disks (DVDs) also called digital versatile
disks are optical disks the same size as CD-ROMs but of
even higher capacity (minimum of 4.7 gigabytes of data).

 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

 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

Magnetic Tape
 Magnetic tape is an older storage technology that
still used for secondary storage of large volumes
of information.
 The principle advantages
– its inexpensiveness, its relative stability and its ability
to store very large quantities of information.
 The disadvantages
– its sequentially stored data and its relative slowness
compared to the speed of secondary storage media.

Tape
 What is tape?
– Magnetically coated plastic ribbon capable of storing
large amounts of data at low cost
– Primarily used for backup

PC Cards
 What is a PC Card?
– Adds capabilities to computer
– Credit-card-sized device
commonly used in notebook
computers

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?
– Data or instructions entered into memory of computer
– Input device is any hardware component that allows
users to enter data and instructions

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

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

Other Pointing Devices Contd…)
 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

Other Pointing Devices Contd…)
 What is a touch screen?
 Often used with kiosks
 Touch areas of screen with finger

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?

Digital Cameras
 How does a digital camera work?

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 camera DV camera used to capture video and
still images, and to make video telephone calls on
Internet
 Also called PC camera
 Web cam video 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?
 Device that uses light source to read characters, marks, and
codes and then converts them into digital data
 Optical character recognition (OCR) reads characters in
OCR font
 Optical mark recognition (OMR) reads hand-drawn pencil
marks, such as small circles

 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
 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).

Output Devices
– 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?
 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?
– Output device that visually conveys information
 Information on display device sometimes
called soft copy
 Monitor houses display device as separate peripheral

Display Devices
 What is a CRT monitor?
– Contains cathode-ray tube (CRT), LCD, LED
– Screen coated with tiny dots of phosphor material
• Each dot consists of a red, blue, and green phosphor
– Common sizes are 15, 17, 19, 21, and 22 inches
• Viewable size is diagonal measurement of actual viewing area

Video Cards
 Video cards plug into the motherboard and are
used to display video.
 VRAM is video memory that enhances the
refreshment rate of the image.
 Video cards have chipsets that can increase the
speed of video display.

Resolution
 Resolution refers to the number of pixels (picture
elements) in the monitor image.
 Increased resolution uses more computer
resources but increases the visual clarity of the
display.

Resolution
 Screen resolution is measured in pixel per inch (ppi), and
printer resolution is measured in dots per inch (dpi).
 Computer screen resolution is approximately 72 ppi.
 Width x Height (Pixels) Video Display
– 640 x 480 Low Resolution
– 800 x 600 Medium Resolution
– 1600 x 1200 High Resolution

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

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

Ports and Peripherals
 Ports are an interface between the computer and
another peripheral device such as a disk drive,
mouse, printer, modem, monitor, camera, FLASH
drive or keyboard.
Examples:
– Serial
– Parallel
– hot-wire
– USB

Troubleshooting
 No display in Monitor
– Check All Power Cable And Monitor VGA Cable
– Clean up the insides of your Pc with a paint brush at
least once a month. (Due to Dust)
– Try hooking up an extra cooling fan to your Pc to
reduce the heat.
– Keep your Pc in a well ventilated area such as close to a
window.

Troubleshooting (Contd…)
 CPU running but no display on monitor
– Clean your CMOS battery which is attached with your
motherboard, this is just like a watch battery and after
you clean it out by rubbing it a little bit put it back in.
– Then clean your RAM by pulling it out and also dust
off your CPU
– Change Your Power Supply
CMOS Battery

 3-beeps-no-display-on-monitor
– Remove the RAM from the slot, clean it and place it
back properly
– Try another slot. Check you RAM also

 Hard disk not detected
 Boot Disk Failure
– Check All Power Cable And SATA Cable

 No Power in CPU
– Check power supply
Green
Ware
Black Ware

 No Network
 No Network icon
– Check your LAN Cable
Connect properly
– Check your LAN Card
Install properly

 Document Not
printing
– Check your Printer is online
– Connect your printer And install
– Driver Properly

 Blue-screen-appears-
and-system-restarts

 At First Check your PC and Antivirus install in
your PC it works Properly or not!
 Change Your Ram
 Change Your Hard disk
 Uninstall related Driver and Software
 Install A Fresh OS WIN-7

Introduction to computer hardware

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Introduction to computer hardware