Computer Hardware
History of computers
Types of computer systems
Hardware components and functions
Computer peripherals
Chapter
3
Electronic computers
• ENIAC – First generation of
electronic computer, 1946
– Used vacuum tubes
– Programmable
– 5000 calculations per second
• Drawbacks:
– size; It occupied more than 1,500
square feet of floor space
– processing ability; it could
process only one program or
problem at a time.
Next wave of computing
• Second generation, late 1950s
– Transistors replace the vacuum tubes
– 200,000 to 250,000 calculations per second
• Third generation, mid 1960s
– Integrated circuitry with miniaturization
• Fourth generation, 1971
– Further miniaturization of circuits
– Increased in Multiprogramming and virtual storage
• Fifth generation, 1980s
– Millions of calculations per second
Microcomputers
• 1975, first microcomputer
– ALTAIR 8800, was programmed
by flicking switches on the front.
• 1977, first personal computers
• 1979, Mass production of the Apple computer, the
fastest selling PC so far.
• 1982, IBM introduces the PC which changes the
market
Computer System Categories
Computer System Categories
• Computer System Categories factors:
– Size
– Processing capability
– Storage capacity
– Computation complexity
Microcomputer Systems
• Personal Computer (PC) : microcomputer for use
by an individual
– Desktop – fit on an office desk
– Laptop – small, portable PC
• Information Appliances: Hand-held microcomputer
devices known as personal digital assistants (PDA)
– E.g. Internet enabled cellular phones
Microcomputer Systems
(Network Computers )
• Network Computers: are low-cost, sealed
microcomputers with no or minimal disk storage that
are linked to the network.
• Users of these Computers depend primarily on network
servers for their operating system and Web browser,
application software, and data access and storage.
• Terminals: modified Network Computers depend on
network servers for software, processing and storage.
• Example: transaction terminals :
• ATM (automated teller machines)
• POS (point-of sale )
Powerful Microcomputer Systems
• Workstation : a powerful Microcomputer, that
support applications with heavy mathematical
computing and graphics display demands, such as
computer-aided design (CAD) in engineering or
investment and portfolio analysis in the securities
industry.
• Network Server : more powerful microcomputers
that coordinate telecommunications and resource
sharing in small networks such as local area
networks (LANs).
Midrange systems
• E.g. High-end network servers:
computers used to coordinate
communications and manage
resource sharing in network settings.
• E.g. Minicomputers for scientific
research and industrial process
monitoring and control.
• Less costly to buy, operate and
maintain than mainframe
Mainframe Computer Systems
• Large, fast powerful computer
systems
– Can process thousands of million
instructions per second (MIPS).
• Large primary storage capacity
• High transaction processing
• Complex computations
• E.g. superservers for large
companies
Mainframe : Supercomputer Systems
• Extremely powerful systems
• Designed for Scientific, engineering and business applications at
extremely high speeds
• Used for applications such as :Global weather forecasting, military
defense, computational cosmology and astronomy, microprocessor
research and design, and large-scale data mining
• Parallel processing with thousands of microprocessors
• Billions of operations per second (gigaflops)
• Supercomputers that calculate in teraflops (trillions of floating-point
operations per second) which use thousands of microprocessors are
now in use.
• Cost millions of dollars
• Minisupercomputers costing hundreds of thousands of dollars
Computer hardware functions
Computer hardware functions
• Input devices:
– E.g. Keyboards, mice, optical scanners
– Convert data into electronic form
• Processing device:
– Central Processing Unit (CPU) consists of:
• Arithmetic-logic unit performs the arithmetic functions
• Control unit
• Output devices:
– E.g. Video display units, printers, etc.
– Convert electronic information into humanintelligible form
Computer hardware functions
• Storage devices:
– Primary Storage Unit or main memory
– E.g. RAM, cache memory
– Secondary Storage
• E.g. Magnetic disks and Optical disks
• Control device:
– Control unit of the CPU
– Controls the other components of the computer
Computer Processing Speeds
• Time as speed unit
•
•
•
•
Millisecond: thousandth of a second
Microsecond: millionth of a second
Nanosecond: billionth of a second
Picosecond: trillionth of a second
• Number of Instructions per second as speed unit
• MIPS : million instructions per second
• Gigaflops: Billions of operations per second
• Teraflops: trillions of floating point operations per second (Supercomputer)
• Clock speed of the computer (the speed of microprocessors’ timing
circuits or internal clock):
• Megahertz (MHz) : millions of cycles per second
• Gigahertz (GHz) : billions of cycles per second
Moore’s Law
Moore observed an
exponential growth
(doubling every 18 to 24
months) in the number of
transistors per integrated
circuit and predicted that
this trend would continue.
Peripherals
• Peripheral is generic name for all input, output,
and secondary storage devices that are part of
the computer system but are not part of the CPU
• Peripherals are online devices; they are separate
from CPU But electronically connected to and
controlled by CPU
• Offline devices: Separate from and not under
control of the CPU
Peripheral Checklist
Input technologies
•
•
•
•
•
Keyboards
Pointing Devices
Optical Scanning
Digital cameras
Speech Recognition Systems
Pointing Devices
• The Pointing Devices work with Graphical user
interface (GUI) using point-and-click or pointand-drag methods.
• GUI (Graphical User Interface): Icons, menus,
windows, buttons and bars
Pointing Devices (2)
• Electronic Mouse
• Trackball
– Stationary device like a mouse
– Roller ball used to move cursor on screen.
• Pointing Stick (also called a trackpoint)
– Small eraser head-like device in keypad
– Moves cursor in direction of pressure placed on
stick.
• Touchpad
– Small rectangular touch-sensitive surface
– Moves the cursor in the direction of finger moves
on the pad
Pointing Devices (3)
• Touch Screen
– Pressure-sensitive Video display
screen
• Pen-based Computing
• Used in Tablet PCs and PDAs
• like touch screen
• Contain fast processors and have
software that digitizes handwriting,
hand printing, and hand drawing
Optical Scanning
• Read text or graphics and convert them into digital
input
• Optical Scanners:
– Compact Desktop scanners (low cost and ease of
use)
– Flatbed scanners (larger, more expensive but
faster and provide higher-resolution color
scanning)
• Optical Character Recognition (OCR) Scanners :
– an optical scanner with sophisticated software can
read the characters and codes on printed or
written text such as merchandise tags, product
labels, credit card receipts, utility bills, airline
tickets, and other documents.
– E.g. handheld optical scanning wands that used to
read bar codes such as the Universal Product
Code (UPC)
Speech Recognition Systems
•System compares speech patterns to database of sound patterns.
• These systems require Training: to recognize your voice patterns; Training
such systems involves repeating a variety of words and phrases
• used to operate your computer’s operating systems and software packages
through voice input of data and commands.
•Speaker independent system: understand voice never heard before
•Used in voice-messaging computers
•Examples include computerized telephone call switching,
telemarketing surveys, bank pay-by-phone bill-paying services, stock
quotation services, university registration systems, and customer
credit and account balance inquiries.
Output Technologies
• Video displays
– Cathode ray tube (CRT) like a television
• old desktop PC screens
– Liquid crystal displays (LCDs)
• Laptop and PDAs, PCs
– Plasma Displays
– LED Displays
• Printed Output
– Inkjet printer: Spray ink on page
– Laser printer : Electrostatic process like photocopying machine
Storage Devices
• Primary Storage
• Semiconductor Memory
• Secondary Storage
• Magnetic Disk
• Optical Disk
• Magnetic Tape
• Storage tradeoffs Factors
• Access Speed
(Semiconductor, Magnetic Disk, Optical Disk, Magnetic Tape)
• Storage capacity (Magnetic Tape, Optical Disk, Magnetic Disk, Semiconductor)
• Cost
(Semiconductor, Magnetic Disk, Optical Disk, Magnetic Tape)
Storage tradeoffs
Computer Storage Fundamentals
• Binary representation
– Data are processed and stored
in computer system through
the presence or absence of
signals or electronic charge.
– Either ON or OFF
• ON = number 1
• OFF = number 0
Bit and Byte
• Bit (short for binary digit)
– Smallest element of data
– Either zero or one
• Byte
– Group of eight bits which operate as a single unit
– Represents one character or number
Representing characters in bytes
• ASCII : (American Standard Code for Information Interchange)
Computers use binary system to calculate
Measuring storage capacities
• Kilobyte (KB): one thousand bytes; 1024 Byte exactly
• Megabyte (MB): one million bytes = 1024 KB
• Gigabyte (GB): one billion bytes
= 1024 MB
• Terabyte (TB): one trillion bytes
= 1024 GB
• Petabyte (PB): one quadrillion bytes = 1024 TB
• Exabyte (EB) : one quintillion bytes = 1024 PB
Direct and Sequential Access
• Direct Access or Random Access
– Directly store and retrieve data
– Each storage position has unique
address and can be accessed in
same length of time
– Semiconductor memory chips,
magnetic disks, optical disk
• Sequential Access
– Data is stored and retrieved in a
sequential process
– Must be accessed in sequence by
searching through prior data
– Magnetic tape
Direct and sequential access
Semiconductor memory
• Microelectronic semiconductor memory chips
• Used for primary storage
• Advantage:
– Small size
– Fast (high access speed)
– Shock and temperature resistance
• Disadvantage:
– Volatility: must have uninterrupted electric power or
lose memory
Two types of semiconductor memory
• RAM: random access memory
– Most widely used primary storage medium
– Volatile memory
– Read/write memory
• ROM: read only memory
– Permanent storage
– Can be read but cannot be overwritten
– Frequently used programs (control instructions in the control
unit and programs in primary storage such as parts of the
operating system) permanently burnt in to the storage cells
during manufacture.
• Variations include:
– PROM (programmable read-only memory)
– EPROM (erasable programmable read-only memory), which can
be permanently or temporarily programmed after manufacture.
Flash drive
• New type of permanent storage
• Uses semiconductor memory
• Small chip with thousands of transistors
• Easily transported
• Also called jump drives, USB flash drives
Source: Courtesy of Lexar Media.
Magnetic Disks
• Used for secondary
storage
• Fast access and high
storage capacity
Types of magnetic disks
• Floppy disks
– Magnetic disk inside a plastic jacket
• Hard disk drives
– Magnetic disk, access arms, and read/write heads in
sealed module
• RAID (Redundant arrays of independent disks)
– Disk arrays of interconnected hard disk drives
– Fault tolerant with multiple copies on several disks
Magnetic Tape
• Secondary storage
• Tape reels and cartridges
• Main purpose of using Magnetic Tape is :
Archival storage and backup storage
Optical Disks
Uses of optical disks
• Publishing medium for fast access to reference
materials
– Catalogs, directories, etc.
• Interactive multimedia applications
– Video games, educational videos, etc.