Transcript Computer Hardware

Computer Hardware
Lecture 1
Management Information System
Chapter Objective
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Identify the major types, trends and uses of microcomputer,
midrange and mainframe computer systems.
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Outline the major technologies and uses of computer
peripherals for input, output and storage
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Identify and give examples of the components and functions of
a computer system
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Identify he computer systems and peripherals you would
acquire or recommend for a business of your choice and
explain the reason or your selections
Computer System Categories
Computer System Categories
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Traditionally, computer systems are classified as Microcomputers, Midrange
computers and Mainframe computers. However, these distinctions are not so clear
as a few years ago. Improvements in technology make microcomputers more
powerful than ever and both minis and mainframes have lower and higher end
versions. Within these parameters, the following are generally true:
Microcomputers. These are the smallest computer systems, ranging in size from
handheld personal digital assistants (PDAs) to laptops to desktop personal
computers. Most microcomputer are designed for single-user application but can
be linked via telecommunications to network servers.
Midrange: Midrange or minicomputers are larger and more powerful that most
microcomputers but smaller and less powerful than most large mainframes.
Midrange systems are often used in business and scientific research. They are
especially well suited for specialized tasks, usually so as to dedicate computing
power to a specific function (such as back room order processing) without having
to share time on an organization's larger mainframe. Of course, many small and
medium-sized organizations use such computer for their whole operations.
Mainframes: These are large, powerful computers (often filling an entire room)
with very large primary storage capacities (from 64 megabytes to several gigabytes
of RAM). This feature helps mainframes process information very quickly (at 10 to
200 million instructions per second - MIPS).
Trends in Computer System Capabilities
Trends in Computer System Capabilities
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A computer system is an interrelated combination of components performing
specialized functions to provide end users with a powerful information-processing tool.
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Computers have radically changed from their early beginnings. As the figure indicates,
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First Generation. First generation computers (1951-1958) used hundreds or thousands of vacuum
tubes for their processing and memory circuitry. These were room size computers that generated a
great deal of heat requiring large air conditioning and maintenance support.
Second Generation. Second generation computers (1959-1963) used transistors and other solidstate semiconductor devices wired to circuit boards. Magnetic cores were used for memory and
removable magnetic disk packs and magnetic tape were used for secondary storage.
Third Generation. Third generation computers (19654-1979) began using integrated circuits
consisting of thousands of transistors and other circuit elements etched on tiny chips of silicon
allowing for increased memory and processing speeds of several millions of instructions per second
(MIPS).
Fourth Generation. Fourth generation computers (1979-present) use large scale integration (LSI)
and very large scale integration (VLSI) that cram hundreds of thousands or millions of transistors
and other circuit elements on each chip.
Fifth Generation. The next generation of computers should continue the trend toward more power,
more speed, smaller size, and longer terms of service. Fifth generation computers may use
superconductor circuits or other developing technologies to process and store information.
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Microcomputer Systems
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Handheld Computers
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PDA, Information
Appliances
Notebook Computers
Desktop Computers
Workstations
Network Server
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Powerful microcomputer
used in small LANs
Microcomputer Systems
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Microcomputers are the most important category of computer systems for businesspeople
and consumers. Though usually called a personal computer, or PC, a microcomputer is much
more than a small computer for use by an individual. The computing power of
microcomputers now exceeds that of the mainframes of previous computer generations at a
fraction of their cost. Thus, they have become powerful networked professional workstations
for business professionals.
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PDA - is a hand-held microcomputer device that enable you to manage information such as
appointments, to-do lists, and sales contacts, send and receive E-mail, access the Web and
exchange such information with your desktop PC or network server.
Information Appliances - Small Web-enabled microcomputer devices with specialized
functions, such as hand-held PDAs, TV set-top boxes, game consoles, cellular and PCS phones,
wired telephone appliances and other Web-enabled home appliances.
Notebook computer - A computer that is designed for those who want a small portable
PC for their work activities.
Desktop computer - A computer that is designed to fit on an office desk.
Workstation - (1) A computer system designed to support the work of one person. (2) a
high-powered computer to support the work of professionals in engineering, science and
other areas that require extensive computing power and graphics capabilities.
Network Servers - These powerful microcomputers are used to coordinate
telecommunications and resource sharing in small local area networks and Internet and
intranet websites.
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Network Computers and Terminals
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Network computers and terminals are emerging as the serious business-computing platform.
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Network Computers. Network computers (NC) are a microcomputer category designed primarily for use with the
Internet and corporate Intranets by clerical workers, operational employees, and knowledge workers. NCs are low cost,
sealed networked microcomputers with no or minimal disk storage. As a result they depend on Internet and Intranet servers
for their operating system and web-browser, Java-enabled application software and data access and storage.
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NC benefits include:
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Lower purchase cost
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Easier maintenance
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Easier software distribution and licensing
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Computer platform standardization
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Reduced end user support requirements
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Improved manageability
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There are two types of Network Computers:
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NCs or Thin Clients. These devices generally have no hard disk. They rely on network servers to provide the operating
system and application software. They typically use a web browser and can process Java-enabled software.
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NetPC. These devices work like a PC with its own software. It may have a hard drive but no floppy drive or CD-ROM. The
operating system and applications are managed centrally by network servers.
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Still another device becoming more popular is the network terminal, or window terminal.
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Network Terminals. Like all terminals, these devices rely on a host processor (server) to perform processing. Hence they
have no disk storage.
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They typically use multiuser versions of windows 2000, Linux, or unit as the operating system.
Computer System Components
Central Processing Unit
Input
Devices
Control
Unit
Special
Purpose
Processors
ALU
Cache
Memory
Secondary
Storage
Devices
Primary
Storage
Output
Output
Devices
Devices
Computer System Components
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A computer system is an interrelated combination of components performing specialized
basic functions to provide end users with a powerful information processing tool. Key
functions include:
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Input: The input devices of a computer system include keyboards, touch screens, pens,
electronic "mice," optical scanners and other peripheral hardware components that convert
electronic data into electronic machine-readable form. Input may be direct entry (by the end
user) or through telecommunications links.
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Processing: The central processing unit (CPU) is the main processing component of a
computer system. A key component of the CPU is the arithmetic-logic unit (ALU), which
performs the arithmetic and logic functions required in computer processing.
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Output: Output devices convert the electronic information produced by the computer
system (binary or digital information) into human-intelligible form for presentation to end
users. Output devices include video display units, printers, audio response units and other
peripheral hardware components specialized in this function.
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Storage: Storage devices store data and programs instructions needed for processing. A
computer's primary storage or memory is used to hold key information needed to run the
computer while secondary storage (such as magnetic disks and tape units) hold larger parts of
programs used less frequently and the content files created by end users.
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Control: The control unit of the CPU interprets computer program instructions and
transmits directions to the other components of the computer system.
Input Technology Trends
First
Generation
Punched
Cards
Paper Tape
Second
Generation
Punched
Cards
Third
Generation
Key to Tape/
Disk
Fourth
Generation
Fifth
Generation
Keyboard Data
Entry
Pointing Devices
Optical Scanning
Voice
Recognition
Touch Devices
Handwriting
Recognition
Trend: Towards Direct Input Devices that Are More Natural
and Easy to Use
Input Technology Trends
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This figure emphasizes that there has been a major trend
toward the increased use of input technologies that provide a
more natural user interface for computer users. You can now
enter data and commands directly and easily into a computer
system through pointing devices like electronic mice and touch
pads, and technologies like optical scanning, handwriting
recognition, and voice recognition. These developments have
made it unnecessary to always record data on paper source
documents (such as sales order forms, for example), and then
keyboard the data into a computer in an additional data entry
step. Further improvements in voice recognition and other
technologies should enable an even more natural user
interface in the future.
Common Input Devices
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Keyboard
Pointing Devices
Pen Based Computing
Speech Recognition
Optical Scanning
Magnetic Ink Character
Recognition
Smart Cards
Digital Cameras
Common Input Devices
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Let’s take a moment to review some of the more popular means and devices used for capturing input.
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Keyboards. Are the most widely used devices for entering data and text.
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Pointing Devices. Are widely used with operating systems that have a graphical user interface. They include a range of devices:
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Electronic mouse
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Trackball
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Pointing stick-- a small button-like device centered on a row above the keyboard in some notebook PCs.
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Touchpads-- rectangular touch-sensitive surface usually below the keyboard, found in notebook PCs
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Touch screens-- devices that allow you to use a computer by touching the face of its video display screen.
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Pen-based Computing Devices. Are used in many handheld computers. These computers use special software to recognize and digitize
handwriting and drawings using a stylus.
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Speech Recognition Systems. Use software to digitize, analyze, and classify your speech and its sound patterns. Recognized words are
then passed to your application software.
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Optical Scanning. Are devices that read text or graphics and convert them into digital input. There are various types of optical scanning
devices including:
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Desktop Scanners-- used with PCs to capture images
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Optical Character Recognition (OCR)-- reads special OCR characters and codes on documents
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Magnetic Ink Character Recognition (MICR). Used by the banking industry to read checks. Uses special ink and a special reader to read
bank and customer identification data written on the bottom of the check.
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Magnetic Stripe. Uses a magnetic stripe on the back of cards to store up to 200 bytes of data. Data is read using a magnetic stripe
reader.
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Smart Cards. Embeds a microprocessor chip with several kilobytes of memory.
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Digital Cameras. Enables you to capture and store still photos or full motion video in digital form.
Output Technology Trends
First
Generation
Punched Cards
Printed Reports
and Documents
Second
Generation
Punched Cards
Printed Reports
and Documents
Third
Generation
Printed Reports
and Documents
Video Displays
Fourth
Generation
Fifth
Generation
Video Displays
Audio Responses
Printed Reports
and Documents
Video Displays
Voice Responses
Hyperlinked
Multimedia
Documents
Trend: Towards Output Methods that Communicate Naturally,
Quickly, and Clearly
Output Technology Trends
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This figure shows you the trends in output media and methods
that have developed over the generations of computing. As
you can see, video displays and printed documents have been,
and still are, the most common forms of output from
computer systems. But other natural and attractive output
technologies such as voice response systems and multimedia
output are increasingly found along with video displays in
business applications.
For example, you have probably experienced the voice and
audio output generated by speech and audio microprocessors
in a variety of consumer products. Voice messaging software
enables PCs and servers in voice mail and messaging systems
to interact with you through voice responses. And of course,
multimedia output is common on web sites of the Internet and
corporate intranets.
Common Output Devices
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Video Output
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CRT
LCD
Printed Output
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Inkjet
Laser
Common Output Devices
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Video displays and printed documents have been, and still are, the most common forms of output
from computer systems. But other natural and attractive output technologies such as voice
response systems and multimedia output are increasingly found along with video displays in business
applications.
Video images can serve as input as well as output. TV signals or photographs can be digitized and
used by the computer. Video displays are the most common type of computer output. Typical video
displays include:
Cathode Rate Tube (CRT). Most video displays use a cathode ray tube technology similar to the
picture tubes used in home TV sets. Although the clarity of the display is dependent upon the
graphic capability of the computer, CRTs are capable of a very high level of clarity. This is especially
important for graphics-intensive work needed in research and development and visual presentations.
Liquid Crystal Displays (LCDs). LCDs are the same technology used in electronic calculators
and digital watches. LCDs can be made small and require very little current to operate, making them
ideal for portable devices.
Plasma Displays. Plasma displays are generated when electrically charged particles of gas are
trapped between glass plates. These displays produce very high quality graphics on a flat service at
faster speeds than LCDs. They are much more expensive than LCD output but necessary in
portable computers that require very high resolution video output, such as full motion video and full
color business presentations.
Printed output on paper is still the most common form of output after video displays.
Inkjet printers: spray ink onto a page one line at a time.
Laser printers: use an electrostatic process similar to a photocopying machine to produce many
pages per minute of high-quality output.
Storage Trends
Primary
Storage
First
Generation
Second
Generation
Third
Generation
Fourth
Generation
Fifth
Generation
Magnetic
Drum
Magnetic
Core
Magnetic
Core
LSI
Semiconductor
Memory Chips
VLSI
Semiconductor
Memory Chips
Trend: Towards Large Capacities Using Smaller Microelectronic Circuits
Secondary
Storage
Magnetic Tape
Magnetic Drum
Magnetic Tape
Magnetic Disk
Magnetic Disk
Magnetic Tape
Magnetic Disk
Optical Disk
Magnetic Tape
Trend: Towards Massive Capacities Using Magnetic and Optical Media
Optical Disk
Magnetic Disk
Storage Trends
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Data and information must be stored until needed using a
variety of storage methods. For example, many people and
organizations still rely on paper documents stored in filing
cabinets as a major form of storage media. However, you and
other computer users are more likely to depend on the
memory circuits and secondary storage devices of computer
systems to meet your storage requirements.
Above figure illustrates major trends in primary and secondary
storage methods. Progress in very-large-scale integration
(VLSI), which packs millions of memory circuit elements on
tiny semiconductor memory chips, is responsible for
continuing increases in the main-memory capacity of
computers. Secondary storage capacities are also expected to
escalate into the billions and trillions of characters, due
primarily to the use of optical media.
Primary & Secondary Storage Media
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Data and information need to be stored after input, during processing, and before output. The figure on the slide illustrates the speed, capacity,
and cost relationships of several alternative primary and secondary storage media. High speed storage media cost more per byte and provide
lower total capacities. Conversely, large-media storage is less expensive but slower. Storage media also differ in how they are accessed by the
computer:
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Direct Access. Primary storage media such as semiconductor memory chips and secondary storage devices like magnetic disks and optical disks
have direct access. This means that any element of data can be directly stored and retrieved by the CPU by selecting and using any of the
locations on the storage media. Each location is unique and is available to the CPU independently of other stored elements.
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Sequential Access. Sequential access storage media such as magnetic tape do not have unique storage addresses. Instead, data must be stored
and retrieved using a sequential or serial process. Locating an individual item of data requires searching from the beginning of the sequence
procedure through all of the data elements that proceed it in the sequence.
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Semiconductor Memory. The primary storage of your computer is composed of microelectronic semiconductor memory chips. This includes
specialized memory like external cache memory and flash memory. There are tow types of semiconductor memory:
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Random Access Memory (RAM). Volatile memory that can be sensed (read) and changed written).
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Read Only Memory (ROM). Nonvolatile memory that are used for permanent storage.
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Magnetic Disk. The most common form of secondary storage consists of metal or plastic disks covered with an iron oxide recording material.
Data are recorded on tracks in the form of magnetized spots to form binary digits. Electromagnetic read/write heads, positioned by access
arms are used to read and write data. The two most popular forms of magnetic disks are floppy disks and hard disks.
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Redundant Arrays of Independent Disks (RAID). Are disk arrays of interconnected microcomputer hard disks to provide many gigabytes of
online storage.
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Magnetic Tape. Sequential access secondary storage that uses read/write heads within magnetic tape drives to read and write data in the form
of magnetized spots on the iron oxide plastic coating of plastic tape. Magnetic tape devices include tape reels and cartridges in mainframes and
midrange systems, and small cassettes or cartridges for PCs. Magnetic tape is most often used for archival storage and backup.
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Optical Disk Storage. Are a popular storage medium for image processing that records data by using a laser to burn pits in a plastic disk and
reads data by using a laser to read the binary codes formed by those pits. There are several different types of optical disks.
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Compact Disk-Read Only Memory (CD-ROM)-- each disk can store more than 600MB.
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Compact Disk Recordable (CD-R)-- Enables users to record their own data once on a CD, and read the data indefinitely.
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Compact Disk Rewriteable (CD-RW)-- Enables users to record and erase (rewrite) data.
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Digital Video Disk (DVD)-- each disk can store from 3.0 to 8.5 GB of data on each side of a compact disk. It is expected that DVD will
replace CD-ROM and CD-RW technologies.
Characteristics of Magnetic Disks
Tracks: Concentric circles
for storing data as magnetized
bits.
Cylinders
Access
Mechanism
Access
Arms
Disks
Read/Write
Heads
Track
Sectors:
Portions of a track
Characteristics of Magnetic Disks
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Magnetic disks are the most common form of secondary storage for modern
computer systems. Magnetic disks are thin metal or plastic disks that are coated on
both sides with an iron oxide recording material. Several disks can be mounted
together vertically to increase storage capacity. Electromagnetic read/write heads
are positioned by access arms between the slightly separated disks to read and
write data on concentric, circular tracks (the unique addresses for each data
element). The most popular forms of magnetic disks include:
Floppy Disks. Also called magnetic diskettes, these consist of polyester film disks
covered with an iron oxide compound. A single disk is mounted and rotates freely
inside a protective flexible or hard plastic jacket. Floppies are extremely portable, a
3.5" disk fitting into a shirt pocket.
Hard Disk Drives. The "hard drive" combines several magnetic disks, access arms,
and read/write heads into a sealed module. This allows higher speeds, greater datarecording densities, and closer tolerances within a sealed, more stable environment.
RAID. RAID stands for redundant arrays of inexpensive disks. They combine from
6 to over 100 small hard disk drives and their microprocessors into a single unit.
RAIDs provide large capacities with high speed access via parallel multiple paths
from many disks. They are also fault tolerant in that more than one copy of the
data exists. If a track, sector, or disks fails, backup is possible from one of the
redundant disks.