I. LECTURE OVERVIEW
Foundation Concepts: Computer Hardware, reviews trends and developments in microcomputer, midrange, and mainframe computer systems; basic computer system concepts; and the major types of technologies used in peripheral devices for computer input, output, and storage.
Computer Systems – Major types of computer systems are summarized in Figure 13.2. A computer is a system of information processing components that perform input, processing, output, storage, and control functions. Its hardware components include input and output devices, a central processing unit (CPU), and primary and secondary storage devices. The major functions and hardware in a computer system are summarized in Figure 13.9
Microcomputer Systems – Microcomputers are used as personal computers, network computers, personal digital assistants, technical workstations, and information appliances. Like most computer systems today, microcomputers are interconnected in a variety of telecommunications networks. This typically includes local area networks, client/server networks, intranets and extranets, and the Internet. Other Computer Systems – Midrange computers are increasingly used as powerful network servers, and for many multiuser business data processing and scientific applications. Mainframe computers are larger and more powerful than most midsize computers. They are usually faster, have more memory capacity, and can support more network users and peripheral devices. They are designed to handle the information processing needs of large organizations with high volumes of transaction processing, or with complex computational problems. Supercomputers are a special category of extremely powerful mainframe computer systems designed for massive computational assignments.
II. LEARNING OBJECTIVES
• Identify the major types, trends, and uses of microcomputer, midrange and mainframe computer systems.
• Outline the major technologies and uses of computer peripherals for input, output, and storage.
• Identify and give examples of the components and functions of a computer system.
• Identify the computer systems and peripherals you would acquire or recommend for a business of your choice, and explain the reasons for your selections.
III. LECTURE NOTES
Section 1: Computer Systems: End User and Enterprise Computing
All computers are systems of input, processing, output, storage, and control components. Technology is evolving at a rapid pace, and new forms of input, output, processing, and storage devices continue to enter the market. Analyzing City of Richmond and Tim Beaty Builders
We can learn a lot about innovative business uses of PDAs from this case. Take a few minutes to read it, and we will discuss it (See City of Richmond and Tim Beaty Builders in Section IX).
TYPES OF COMPUTER SYSTEMS -[Figure 13.2]
There are several major categories of computer systems with a variety of characteristics and capabilities. Thus, computer systems are typically classified as:
• Mainframe computers
• Midrange computers
These categories are attempts to describe the relative computing power provided by different computing platforms or types of computers therefore, they are not precise classifications. Some experts predict the merging or disappearance of several computer categories. They feel that many midrange and mainframe systems have been made obsolete by the power and versatility of client/server networks of microcomputers and servers. Most recently, some industry experts have predicted that the emergence of network computers and information appliances for applications on the Internet and corporate intranets will replace many personal computers, especially in large organisations and in the home computer market.
Microcomputers are the smallest but most important categories of computers systems for business people and consumers. They are also referred to as personal computers (or PCs). The computing power of current microcomputers exceeds that of the mainframe computers of previous generations at a fraction of their cost. They have become powerful-networked professional workstations for use by end users in business.
Microcomputers categorised by size
Microcomputers categorised by use
5. Multi-user Systems
Microcomputers categorised by special purpose
1. Workstation Computers
2. Network Servers
3. Personal Digital Assistants
Workstation Computers – some microcomputers are powerful workstation computers (technical work stations) that support applications with heavy mathematical computing and graphics display demands such as computeraided design (CAD) in engineering, or investment and portfolio analysis in the securities industry. Network Servers – are usually more powerful microcomputers that co-ordinate telecommunications and resource sharing in small local area networks (LANs), and Internet and intranet websites. This is the fastest growing microcomputer application category.
• Network Computers (NCs) are a major new microcomputer category designed primarily for use with the Internet and corporate intranets by clerical workers, operational employees, and knowledge workers with specialised or limited computing applications.
In-between NCs and full-featured PCs are stripped-down PCs known as NetPCs or legacy-free PCs. NetPCs are designed for the Internet and a limited range of applications within a company. Examples are: Dell’s Webpc, Compaq’s IPaq, HP’s e-PC, and eMachine’s eOne.
Network computers (also called thin clients) are low-cost, sealed, networked microcomputers with no or minimal disk storage. Users of network computers depend primarily on Internet and intranet servers for their operating system and web browser, Java-enabled application software, and data access and storage. Main attractions of network computers over full-featured PCs are their low cost to:
Other benefits to businesses include:
• Ease of software distribution and licensing
• Computing platform standardisation
• Reduced end user support requirements
• Improved manageability through centralised management and enterprisewide control of computer network resources.
The market is offering a number of gadgets and information appliances that offer users the capability to perform enable host of basic computational chores. Examples of some information appliances include: • Personal Digital Assistants – (PDAs) are designed for convenient mobile communications and computing. PDAs use touch screens, pen-based handwriting recognition, or keyboards to help mobile workers send and receive E-mail, access the Web, and exchange information such as appointments, to-do lists, and sales contacts with their desktop PCs or web servers.
• Set-top boxes and video-game consoles that connect to home TV sets. These devices enable you to surf the Web or send and receive E-mail and watch TV programs or play video games at the same time.
• Wireless PDAs and cellular and PCS phones and wired telephone-based appliances that can send and receive E-mail and access the Web.
Computer terminals are undergoing a major conversion to networked computer devices. For example: • Dumb terminals are keyboard/video monitor devices with limited processing capabilities, to intelligent terminals, which are modified networked PCs, network computers or other microcomputer-powered network devices. Intelligent terminals can perform data entry and some information processing tasks independently. • Networked terminals which may be Windows terminals that are dependent on network servers for Windows software, processing power, and storage, or Internet terminals, which depend on Internet or intranet website servers for their operating systems and application software. • Transaction terminals are a form of intelligent terminal. Uses can be found in banks retail stores, factories, and other work sites. Examples are ATM’s, factory production recorders, and POS terminals.
MIDRANGE COMPUTER SYSTEMS
Midrange computers, including minicomputers and high-end network servers, are multi-user systems that can manage networks of PCs and terminals. Characteristics of midrange computers include:
• Generally, midrange computers are general-purpose computers that are larger and more powerful than most microcomputers but are smaller and less powerful than most large mainframes.
• Cost less to buy, operate, and maintain than mainframe computers.
• Have become popular as powerful network servers to help manage large Internet websites, corporate intranets and extranets, and client/server networks.
• Electronic commerce and other business uses of the Internet are popular high-end server applications, as are integrated enterprisewide manufacturing, distribution, and financial applications.
• Data warehouse management, data mining, and online analytical processing are contributing to the growth of high-end servers and other midrange systems.
• First became popular as minicomputers for scientific research, instrumentation systems, engineering analysis, and industrial process monitoring and control. Minicomputers could easily handle such uses because these applications are narrow in scope and do not demand the processing versatility of mainframe systems.
• Serve as industrial process-control and manufacturing plant computers and they play a major role in computeraided manufacturing (CAM).
• Take the form of powerful technical workstations for computer-aided design (CAD) and other computation and graphics-intensive applications.
• Are used as front-end computers to assist mainframe computers in telecommunications processing and network management.
• Can function in ordinary operating environments (do not need air conditioning or electrical wiring). • Smaller models of minicomputers do not need a staff of specialists to operate them.
MIDRANGE COMPUTER APPLICATIONS
Serve as industrial process-control and manufacturing plant computers. Play a major role in computer-aided manufacturing (CAM).
Serve as powerful technical workstations for computer-aided design (CAD) and other computation and graphics-intensive applications
Serve as front-end computers to assist mainframe computers in telecommunications processing and network management.
Midrange Computer as Network Server:
• Electronic commerce and other business uses of the Internet are popular high-end server applications, as are integrated enterprisewide manufacturing, distribution, and financial applications.
• Other applications, like data warehouse management, data mining, and online analytical processing are contributing to the growth of high-end servers and other midrange systems.
• Serve as powerful network servers to help manage large Internet web sites, corporate Intranets and extranets, and client/server networks
MAINFRAME COMPUTER SYSTEMS
Mainframe computers are large, fast, and powerful computer systems. Characteristics of mainframe computers include:
• They are physically larger and more powerful than micros and minis.
• Can process hundreds of millions of instructions per second (MIPS).
• Have large primary storage capacities. Main memory capacity can range from hundreds of megabytes to many gigabytes of primary storage.
• Mainframes have slimmed down drastically in the last few years, dramatically reducing air-conditioning needs, electronic power consumption, and floor space requirements, and thus their acquisition and operating costs.
• Sales of mainframes have increased due to cost reductions and the increase in applications such as data mining and warehousing, decision support, and electronic commerce.
Mainframe Computer Applications:
• Handle the information processing needs of major corporations and government agencies with many employees and customers.
• Handle enormous and complex computational problems.
• Used in organisations processing great volumes of transactions.
• Handle great volumes of complex calculations involved in scientific and engineering analyses and simulations of complex design projects.
• Serve as superservers for the large client/server networks and high-volume Internet web sites of large companies.
• Are becoming a popular business-computing platform for data mining and warehousing, and electronic commerce applications.
The term supercomputer describes a category of extremely powerful computer systems specifically designed for scientific, engineering, and business applications requiring extremely high-speeds for massive numeric computations.
• Used by government research agencies, large universities, and major corporations.
• Are used for applications such as global weather forecasting, military defence systems, computational cosmology and astronomy, microprocessor research and design, large scale data mining, large time-sharing networks, and so on.
• Use parallel processing architectures of interconnected microprocessors (which can execute many instructions at the same time in parallel).
• Can perform arithmetic calculations at speeds of billions of floating-point operations per second (gigaflops). Teraflop (1 trillion floating-point operations per second) supercomputers, which use advanced massively parallel processing (MPP) designs of thousands of interconnected microprocessors, are becoming available. • Purchase price for large supercomputers are in the $5 million to $50 million range.
The use of symmetric multiprocessing (SMP) and distributed shared memory (DSM) designs of smaller numbers of interconnected microprocessors has spawned a breed of mini-supercomputer with prices that start in the hundreds of thousands of dollars.
TECHNICAL NOTE: THE COMPUTER SYSTEM CONCEPTS – [Figure 13.9]
As a business professional, you do not need a detailed technical knowledge of computers. However, you do need to understand some basic facts and concepts about computer systems. This should help you be an informed and productive user of computer system resources.
A computer is a system, an interrelated combination of components that perform the basic system functions of input, processing, output, storage, and control, thus providing end users with a powerful information-processing tool. Understanding the computer as a computer system is vital to the effective use and management of computers. A computer is a system of hardware devices organised according to the following system functions:
• Input. Examples of some input devices of a computer system include:
2. Touch Screens3. Light Pens
4. Electronic Mice
4. Optical Scanners
5. Voice Input
They convert data into electronic machine-readable form for direct entry or through a telecommunications network into a computer system.
Processing. The central processing unit (CPU) is the main processing component of a computer system. (In microcomputers, it is the main microprocessor). One of the CPU’s major components is the arithmetic-logic unit (ALU) that performs the arithmetic and logic functions required in computer processing. Components of the CPU include:
1. Control Unit 2. Arithmetic-Logic Unit 3. Primary Storage Unit
Output. Convert electronic information produced by the computer system into human-intelligible form for presentation to end-users.
Examples of output devices include:
1. Video Display Units 2. Audio Response Units 3. Printers
Storage. The storage function of a computer system is used to store data and program instructions needed for processing.
Storage devices include:
1. Primary Storage Unit (main memory)
2. Secondary Storage Devices (magnetic disk and tape units, optical disks)
Control. The control unit of a CPU interprets computer program instructions and transmits directions to the other components of the computer system.
Computer Processing Speeds:
Operating speeds of computers are measured in a number of ways. For example: • Milliseconds – Thousands of a second.
Microseconds – Millionths of a second.
Nanoseconds – Billionth of a second
Picosecond – Trillionth of a second
Other terminology used includes:
Teraflop – used by some supercomputers
MIPS – Million instructions per second
Megahertz (MHz) – Millions of cycles per second
Gigahertz (GHz) – Billions of cycles per second
Clock Speed – used to rate microprocessors by the speed of their timing circuits and internal clock.
Section II: Computer Peripherals: Input, Output, and Storage Technologies
A computer is just a high-powered “processing box” without peripherals. Your personal computing needs will dictate the components you choose for our particular computing needs. Analyzing United Technologies and Eastman Kodak
We can learn a lot about the business value of consolidating computer operations and systems from this case. Take a few minutes to read it, and we will discuss it (See United Technologies and Eastman Kodak in Section IX).
Peripherals are the generic name for all input, output, and secondary storage devices that are part of a computer system. Peripherals depend on direct connections or telecommunications links to the central processing unit of a computer system. Thus, all peripherals are online devices, that is, separate from, but can be electronically connected to and controlled by, a CPU. This is the opposite of off-line devices, which are separate from and not under the control of the CPU.
There has been a major trend toward the increased use of input technologies that provide a more natural user interface for computer users. More and more data and commands are being entered directly and easily into computer systems through pointing devices like electronic mice and touch pads, and technologies like optical scanning, handwriting recognition, and voice recognition.
Keyboards are still the most widely used devices for entering data and text into computer systems. However, pointing devices are a better alternative for issuing commands, making choices, and responding to prompts displayed on your video screen. They work with your operating system’s graphical user interface (GUI), which presents you with icons, menus, windows, buttons, bars, and so on, for your selection. Examples of pointing devices include:
• Electronic Mouse – A device used to move the cursor on the screen, as well as to issue commands and make icon and menu selections.
• Trackball – A device used to move the cursor on the display screen.
Pointing Stick – A small buttonlike device, sometimes likened to the eraser head of a pencil. The cursor moves in the direction of the pressure you place on the track point. Touchpad – A small rectangular touch-sensitive surface usually placed below the keyboard. The cursor moves in the direction your finger moves on the pad.
Touch Screens – A device that accepts data input by the placement of a finger on or close to the CRT screen.
Pen-based computing technologies are being used in many hand-held computers and personal digital assistants. These small PCs and PDAs contain fast processors and software that recognises and digitises handwriting, hand printing, and hand drawing. They have a pressure-sensitive layer like a graphics pad under their slatelike liquid crystal display (LCD) screen.
A variety of penlike devices are available:
Digitizer Pen – A photoelectronic device that can be used as a pointing device, or used to draw or write on a pressure-sensitive surface of a graphics tablet.
Graphics Tablet – A device that allows an end user to draw or write on a pressure-sensitive tablet and has their handwriting or graphics digitised by the computer and accepted as input.
SPEECH RECOGNITION SYSTEMS
Speech recognition and voice response (in their infancy) promise to be the easiest method of data entry, word processing, and conversational computing, since speech is the easiest, most natural means of human communication.
Speech recognition systems analyse and classify speech or vocal tract patterns and convert them into digital codes for entry into a computer system. Early voice recognition products used discrete speech recognition, where you had to pause between each spoken word. New continuous speech recognition (CSR) software recognises controlled, conversationally paced speech. Examples of continuous speech recognition software include: • NaturallySpeaking by Dragon Systems
• ViaVoice by IBM
• VoiceXpress by Lernout & Hauspie
• FreeSpeech by Philips
Areas where speech recognition systems are used include:
• Manufacturers use it for inspection, inventory, and quality control
• Airlines and parcel delivery companies use it for voice-directed sorting of baggage and parcels
• Voice activated GPS systems are being used in advanced car design
• Physicians use it to enter and printout prescriptions
• Gemmologists use it to free up their hands when inspecting and grading precious stones
• Handicapped individuals use voice-enabled software to operate their computers, e-mail, and surf the World Wide Web.
Speaker-independent voice recognition systems allow a computer to understand a few words from a voice it has never heard before. They enable computers to respond to verbal and touch-tone input over the telephone.
• Computerized telephone call switching
• Telemarketing surveys
• Bank pay-by-phone bill-paying services
• Stock quotations services
• University registration systems
• Customer credit and account balance inquiries
Optical scanning devices read text or graphics and convert them into digital input for a computer. Optical scanning enables the direct entry of data from source documents into a computer system.
Popular uses of optical scanning include:
• Scanning pages of text and graphics into your computer for desktop publishing and web publishing applications.
• Scan documents into your system and organize them into folders as part of a document management library system for easy reference or retrieval. There are many types of optical scanners, but they all employ photoelectric devices to scan the characters being read. Reflected light patterns of the data are converted into electronic impulses that are then accepted as input into the computer system.
Optical scanning technology known as optical character recognition (OCR) can read special-purpose characters and codes. OCR scanners are used to read characters and codes on:
Credit card receipts
Process business and government forms
Devices such as handheld optical scanning wands are used to read OCR coding on merchandise tags and other media. Many business applications involve reading bar code, a code that utilises bars to represent characters. One common example is the Universal Produce Code (UPC) bar coding that you see on packages of food items and many other products.
OTHER INPUT TECHNOLOGIES
Magnetic stripe technology is a familiar form of data entry that helps computers read credit cards. The dark magnetic stripe on the back of such cards is the same iron oxide coating as on magnetic tape. Smart cards that embed a microprocessor chip and several kilobytes of memory into debit, credit, and other cards are popular in Europe, and becoming available in the United States. Digital cameras and digital video cameras enable you to shoot, store, and download still photos or full motion video with audio into your PC.
Magnetic ink character recognition (MICR) is machine recognition of characters printed with magnetic ink. Primarily used for check processing by the banking industry.
Computers provide information in a variety of forms. 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 displays are the most common type of computer output. Most desktop computers rely on video monitors that use cathode ray tube (CRT) technology. Usually, the clarity of the video display depends on the type of video monitor you use and the graphics circuit board installed in your computer. A high-resolution, flicker-free monitor is especially important if you spend a lot of time viewing multimedia on CDs or the Web, or complex graphical displays of many software packages.
The biggest use of liquid crystal displays (LCDs) is to provide a visual display capability for portable microcomputers and PDAs. LCD displays need significantly less electric current and provide a thin, flat display.
Advances in technology such as active matrix and dual scan capabilities have improved the color and clarity of LCD displays.
After video displays, printed output is the most common form of output displays. Most personal computer systems rely on inkjet or laser printers to produce permanent (hard copy) output in high-quality printed form. Printed output is still a common form of business communications, and is frequently required for legal documentation. • Inkjet printers – Spray ink onto a page one line at a time. They are popular, low-cost printers for microcomputer systems. They are quiet, produce several pages per minute of high-quality output, and can print both black-and-white and high-quality colour graphics.
Laser Printers – Use an electrostatic process similar to a photocopying machine to produce many pages per minute of high-quality black-and-white output. More expensive colour laser printers and multifunction inkjet and laser models that print, fax, scan, and copy are other popular choices for business offices.
Data and information need to be stored after input, during processing, and before output. Computer-based information systems rely primarily on the memory circuits and secondary storage devices of computer systems to accomplish the storage function.
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, are 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. Storage Trade-offs: Speed, capacity, and cost relationships.
• Note the cost/speed/capacity trade-offs as one moves from semiconductor memories to magnetic media, such as magnetic disks and tapes, to optical disks.
• High-speed storage media cost more per byte and provide lower capacities.
• Large capacity storage media cost less per byte but are slower
• Semiconductor memories are used mainly for primary storage, though they are sometimes used as high-speed secondary storage devices.
• Magnetic disk and tape and optical disk devices are used as secondary storage devices to greatly enlarge the storage capacity of computer systems.
• Most primary storage circuits use RAM (random access memory) chips, which lose their contents when electrical power is interrupted
• Secondary storage devices provide a more permanent type of storage media for storage of data and programs.
Computer Storage Fundamentals: [Figure 13.20]
Data is processed and stored in a computer system through the presence or absence of electronic or magnetic signals in the computer’s circuitry in the media it uses. This is called a “two-state” or binary representation of data, since the computer and media can exhibit only two possible states or conditions – ON (1) or OFF (0).
Computer storage elements:
• Bit – is the smallest element of data, (binary digit) which can have a value of zero or one. The capacity of memory chips is usually expressed in terms of bits.
Byte – is the basic grouping of bits that the computer operates as a single unit. It typically consists of 8 bits and is used to represent one character of data in most computer coding schemes (e.g. 8 bits = 1 byte). The capacity
of a computer’s memory and secondary storage devices is usually expressed in terms of bytes. ASCII (American Standard Code for Information Interchange)
EBCDIC (Extended Binary Coded Decimal Interchange Code) Pronounced: EB SEE DICK
Storage capacities are frequently measured in:
= 1,000 bytes
= 1,000,000 bytes
= 1,000,000,000 bytes
= 1,000,000,000,000 bytes
= 1,000,000,000,000,000 bytes
= 1,000,000,000,000,000,000 bytes
= 1,000,000,000,000,000,000,000 bytes
= 1,000,000,000,000,000,000,000,000 bytes
Direct and Sequential Access
• Direct Access – Primary storage media such as semiconductor memory chips are called direct access or random access memories (RAM). Magnetic disk devices are frequently called direct access storage devices (DASDs).
The terms direct access and random access describe the same concept. They mean that an element of data or instructions can be directly stored and retrieved by selecting and using any of the locations on the storage media. They also mean that each storage position (1) has a unique address and (2) can be individually accessed in approximately the same length of time without having to search through other storage positions.
Sequential Access – sequential access storage media such as magnetic tape do not have unique storage addresses that can be directly addressed. Instead, data must be stored and retrieved using a sequential or serial process. Data are recorded one after another in a predetermined sequence on a storage medium. Locating an individual item of data requires searching much of the recorded data on the tape until the desired item is located.
The primary storage (main memory) on most modern computers consists of microelectronic semiconductor memory circuits. Plug-in memory circuit boards containing 32 megabytes or more of memory chips can be added to your PC to increase its memory capacity. Specialized memory can help improve your computer’s performance. Examples include:
• External cache memory of 512 kilobytes to help your microprocessor work faster
• Video graphics accelerator cards with 16 megabytes of RAM are used for faster and clearer video performance
• Removable credit-card-size and smaller “flash memory” RAM cards provide several megabytes of erasable direct access storage for PDAs or hand-held PCs.
Some of the major attractions of semiconductor memory are:
• Small size
• Fast speed
• Shock and temperature resistance
One major disadvantage of most semiconductor memory is:
• Volatility – Uninterrupted electric power must be supplied or the contents of memory will be lost (except with read only memory, which is permanent).
There are two basic types of semiconductor memory:
• Random Access Memory (RAM) – these memory chips are the most widely used primary storage medium. Each memory position can be both read and written, so it is also called read/write memory. This is a volatile memory.
• Read Only Memory (ROM) – Non-volatile random access memory chips are used for permanent storage. ROM can be read but not erased or overwritten. Instructions and programs in primary storage can be permanently “burned in” to the storage cells during manufacturing. This permanent software is also called firmware. Variations include PROM (programmable read only memory) and EPROM (erasable programmable read only memory), which can be permanently or temporarily programmed after manufacture.
MAGNETIC DISK STORAGE
These are the most common forms of secondary storage for modern computer systems. That’s because they provide fast access and high storage capacities at a reasonable cost. Characteristics of magnetic disks:
• Disk drives contain metal disks that are coated on both sides with an iron oxide recording material.
• Several disks are mounted together on a vertical shaft, which typically rotates the disks are speeds of 3,600 to 7,600 revolutions per minute (rpm)
• Access arms between the slightly separated disks to read and write data on concentric, circular tracks position electromagnetic read/write heads.
• Data are recorded on tracks in the form of tiny magnetized spots to form the binary digits of common computer codes.
• Thousands of bytes can be recorded on each track, and there are several hundred data tracks on each disk surface, which provides you with billions of storage positions for software and data. Types of Magnetic Disks
There are several types of magnetic disk arrangements, including disk cartridges as well as fixed disk units. Removable disk devices are popular because they are transportable and can be used to store backup copies of your data off-line for convenience and security.
Floppy Disks, or magnetic disks, 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, which has access openings to accommodate the read/write head of a disk drive unit. The 3-1/2-inch floppy disk, with capacities of 1.44 megabytes, is the most widely used version, with a newer Superdisk technology offering 120 megabytes of storage. Hard Disk Drives combine magnetic disks, access arms, and read/write heads into a sealed module. This allows higher speeds, greater data-recording densities, and closer tolerances within a sealed, more stable environment. Fixed or removable disk cartridge versions are available. Capacities of hard drives range from several hundred megabytes to many gigabytes of storage.
Disk arrays of interconnected microcomputer hard disk drives have replaced large-capacity mainframe disk drives to provide many gigabytes of online storage. Known as RAID (redundant arrays of independent disks), they combine from 6 to more than 100 small hard disk drives and their control microprocessors into a single unit. Advantages of RAID disks include:
• Provide large capacities with high access speeds since data is accessed in parallel over multiple paths from many disks.
• Provide fault tolerant capability, since their redundant design offers multiple copies of data on several disks. If one disk fails, data can be recovered from backup copies automatically stored on other disks. • Storage area networks (SANs) are high-speed fibre channel local area networks that can interconnect many RAID units and share their combined capacity through network servers for many users.
MAGNETIC TAPE STORAGE
Magnetic Tape is still being used as a secondary storage medium in business applications. The read/write heads of magnetic tape drives record data in the form of magnetised spots on the iron oxide coating of the plastic tape. Magnetic tape devices include tape reels and cartridges in mainframes and midrange systems, and small cassettes or cartridges for PCs.
These devices serve as slower, but lower cost, storage to supplement magnetic disks to meet massive data warehouse and other business storage requirements. Other major applications for magnetic tape include long-term archival storage and backup storage for PCs and other systems.
OPTICAL DISK STORAGE
Optical disk storage involves technology, which is based on using a laser to
read tiny spots on a plastic disk. The disks are currently capable of storing billions of characters of information.
• CD-ROM – A common type of optical disk used on microcomputers. They are used for read only storage. Storage is over 600 megabytes per disk. This is equivalent to over 400 1.44-megabyte floppy disks or 300,000 double-spaced pages of text. Data are recorded as microscopic pits in a spiral track, and are read using a laser device.
Limitation: Recorded data cannot be erased
• CD-R – (Compact disk recordable) is another optical disk technology. It enables computers with CD-R disk drive units to record their own data once on a CD, and then be able to read the data indefinitely. Limitation: Recorded data cannot be erased
• CD-RW – (CD-rewritable) optical disk systems have now become available which record and erase data by using a laser to heat a microscopic point on the disk’s surface. In CD-RW versions using magneto-optical technology, a magnetic coil changes the spot’s reflective properties from one direction to another, thus recording a binary one to zero. A laser device can then read the binary codes on the disk by sensing the direction of reflected light.
• DVD – (Digital Video Disk or Digital Versatile Disk) can hold from 3.0 to 8.5 gigabytes of multimedia data on each side of a compact disk. The large capacities and high- quality images and sound of DVD technology are expected to eventually replace CD-ROM and CD-RW technologies for data storage, and promise to accelerate the use of DVD drives for multimedia products that can be used in both computers and home entertainment systems.
• DVD-ROM is beginning to replace magnetic tape videocassettes for movies and other multimedia products.
• DVD – RAM is being used for backup and archival storage data and multimedia files.
One of the major uses of optical disks in mainframe and midrange systems is in image processing, where longterm archival storage of historical files of document images must be maintained. Mainframe and midrange computer versions of optical disks use 12-inch plastic disks with capacities of several gigabytes, with up to 20 disks held in jukebox drive units. WORM – (Write Once, Read Many) versions of optical disks are used to store data on the disk. Although data can only be stored once, it can be read an infinite number of times.
One of the major business uses of CD-ROM disks for personal computers is to provide a publishing medium for fast access to reference materials in a convenient, compact form. These include:
• Periodical abstracts
• Part listings
• Statistical databases of business activity and economic activity Interactive multimedia applications in business, education, and entertainment using
CD-ROM and DVD disks.
Optical disks have become a popular storage medium for image processing and multimedia business applications and they appear to be a promising alternative to magnetic disks and tape for very large mass storage capabilities for enterprise computing systems. However, rewritable optical technologies are still being perfected. Also, most optical disk devices are significantly slower and more expensive (per byte of storage) than magnetic disk devices. So optical disk systems are not expected to displace magnetic disk technology in the near future for most business applications.
IV. KEY TERMS AND CONCEPTS – DEFINED
Pertaining to the presence or absence of electronic or magnetic “signals” in the computer’s circuitry or in the media it uses. There are only two possible states or conditions – presence or absence. Central Processing Unit (CPU):
The unit of a computer system that includes the circuits that controls the interpretation and execution of instructions. In many computer systems, the CPU includes the arithmetic-logic unit, the control unit, and primary storage unit.
Computer hardware as a system of input, processing, output, storage, and control components. Thus a computer system consists of input and output devices, primary and secondary storage devices, the central processing unit, the control unit within the CPU, and other peripheral devices.
Any input/output device connected by telecommunications links to a computer.
Digital still cameras and digital video cameras enable you to shoot, store, and download still photos or full-motion video with audio in your PC.
A method of storage where each storage position has a unique address and can be individually accessed in approximately the same period of time without having to search through other storage positions. Information Appliance:
Devices for consumers to access the Internet.
A small portable PC.
Liquid Crystal Displays (LCD):
Electronic visual displays that form characters by applying an electrical charge to selected silicon crystals.
Magnetic Disk Storage:
Data storage technology that uses magnetised spots on metal or plastic disks. Magnetic Disk Storage – Floppy Disk:
Small phonograph record enclosed in a protective envelope. It is a widely used form of magnetic disk media that provides a direct access storage capability for microcomputer systems. Magnetic Disk Storage – Hard Disk
Secondary storage medium; generally nonremovable disks made out of metal and covered with a magnetic recording surface. It holds data in the form of magnetised spots.
Magnetic Disk Storage – RAID
Redundant array of independent disks. Magnetic disk units that house many interconnected microcomputer hard disk drives, thus providing large, fault tolerant storage capacities. Magnetic Ink Character Recognition (MICR):
The machine recognition of characters printed with magnetic ink. Primarily used for check processing by the banking industry.
A magnetic stripe card is a plastic wallet-size card with a strip of magnetic tape on one surface; widely used for credit/debit cards.
A plastic tape with a magnetic surface on which data can be stored by selective magnetisation of portions of the surface.
A larger-size computer system, typically with a separate central processing unit, as distinguished from microcomputer and minicomputer systems.
A very small computer, ranging in size from a “Computer on a chip” to a small typewriter-size unit. Microprocessor:
A semiconductor chip with circuitry for processing data.
Larger and more powerful than most microcomputers but are smaller and less powerful than most large mainframe computer systems.
A small electronic general-purpose computer.
A new category of microcomputer designed mainly for use with the Internet and Intranets on tasks requiring limited or specialised applications and no or minimal disk storage. Network Server:
A type of midrange computer used to co-ordinate telecommunications and resource sharing and manages large web sites, Intranets, extranets, and client/server networks.
A terminal that depends on network servers for its software and processing power. Off-line:
Pertaining to equipment or devices not under control of the central processing unit. Online:
Pertaining to equipment or devices under control of the central processing unit. Optical Character Recognition (OCR):
The machine identification of printed characters through the use of light-sensitive devices. Optical Disk Storage:
Technology based on using a laser to read tiny spots on a plastic disk. The disks are currently capable of storing billions of characters of information.
Optical Disk Storage – CD-ROM:
An optical disk technology for microcomputers featuring compact disks with a storage capacity of over 500 megabytes.
Optical Disk Storage – CD-R:
Compact disk recordable (CD-R) enables computers with CD-R disk drive units to record their own data once on a CD, than be able to read the data indefinitely.
Optical Disk Storage – CD-RW:
Compact disk rewritable (CD-RW) enables computers with CD-RW disk drive units to record and erase data by using a laser to heat a microscopic point on the disk’s surface. Optical Disk Storage – DVD:
Digital video disk or digital versatile disk (DVD) enables computers with DVD disk drive units to hold from 3.0 to 8.5 gigabytes of multimedia data on each side of a compact disk. Optical Disk Storage – WORM Disk:
Optical disk that allows users to write once, read many times.
Using a device (scanner) that scans characters or images and generates their digital representations. Pen-Based Computing:
Tablet-style microcomputers that recognise hand-writing and hand-drawing done by a pen-shaped device on their pressure sensitive display screens.
In a computer system, any unit of equipment, distinct from the central processing unit, that provides the system with input, output, or storage capabilities.
Personal Digital Assistant:
Handheld microcomputer devices, which are designed for convenient mobile communications and computing. Pointing Devices:
Devices, which allow end users to issue commands or make choices by moving a cursor on the display, screen. Pointing Device – Electronic Mouse:
A small device that is electronically connected to a computer and is moved by hand on a flat surface in order to move the cursor on a video screen in the same direction. Buttons on the mouse allow users to issue commands and make responses or selections.
Pointing Device – Pointing Stick:
A small buttonlike device sometimes likened to the eraser head of a pencil. The cursor moves in the direction of the pressure you place on the track point.
Pointing Device – Touchpad:
Is a small rectangular touch-sensitive surface usually placed below the keyboard. The cursor moves in the direction your finger moves on the pad.
Pointing Device – Trackball:
A roller device set in a case used to move the cursor on a computer’s display screen. Primary Storage:
The main (or internal) memory of a computer. Usually in the form of semiconductor storage. Printers:
Devices that produce hard copy output such as paper documents or reports. Secondary Storage:
External or auxiliary storage device that supplements the primary storage of a computer.
Microelectronic storage circuitry etched on tiny chips of silicon or other semiconducting material.
Semiconductor Memory – RAM:
Also known as main memory or primary storage; type of memory that temporarily holds data and instructions needed shortly by the CPU. RAM is a volatile type of storage. Semiconductor Memory – ROM:
Also known as firmware; a memory chip that permanently stores instructions and data that are programmed during the chip’s manufacture. Three variations on the ROM chip are PROM, EPROM, and EEPROM. ROM is a nonvolatile form of storage. Sequential Access:
A sequential method of storing and retrieving data from a file.
Cards such as debit and credit cards, which have an embedded microprocessor
chip and several kilobytes of memory.
Direct conversion of spoken data into electronic form suitable for entry into a computer system. Promises to be the easiest, most natural way to communicate with computers.
Storage Capacity Elements:
Units used for storage capacity and data: bits, bytes, kilobytes (KB), megabytes (MB), gigabytes (GB), terabytes (TB).
Storage Capacity Elements – Bit:
A contraction of “binary digit”. It can have the value of either 0 or
1. Storage Capacity Elements – Byte:
A sequence of adjacent binary digits operated on as a unit and usually shorter than a computer word. In many computer systems, a byte is a grouping of eight bits that can represent one alphabetic or special character or can be “packed” with two decimal digits.
Storage Capacity Elements – Kilobyte (K or KB):
When referring to computer storage capacity it is equivalent to 2 to the 10th power, or 1,014 in decimal notation.
Storage Capacity Elements – Megabyte (MB):
One million bytes. More accurately, 2 to the 20th power, 1,048,576 in decimal notation.
Storage Capacity Elements – Gigabyte (GB):
One billion bytes. More accurately, 2 to the 30th power, or 1,073,741,824 in decimal notation.
Storage Capacity Elements – Terabyte (TB):
One trillion bytes. More accurately, 2 to the 40th power, or 1,009,511,627,776 in decimal notation.
Storage Media Trade-offs:
The trade-offs in cost, speed, and capacity of various storage media.
A special category of large computer systems that are the most powerful available. They are designed to solve massive computational problems.
Units used for measuring processing speeds: milliseconds, microseconds, nanoseconds, and picoseconds.
Time Elements – Millisecond:
A thousandth of a second.
Time Elements – Microsecond:
A millionth of a second.
Time Elements – Nanosecond:
One billionth of a second.
Time Elements – Picosecond:
One trillionth of a second.
An input device that accepts data input by the placement of a finger on or close to the CRT screen.
Terminals used in banks, retail stores, factories, and other work sites that are used to capture transaction data at their point of origin. Examples are point-of-sale (POS) terminals and automated teller machines (ATMs).
Video displays are the most common type of computer output.
Memory (such as electronic semiconductor memory) that loses its contents when electrical power is interrupted. Wand:
A handheld optical character recognition device used for data entry by many transaction terminals. Workstation:
A computer terminal or micro- or minicomputer system designed to support the work of one person. Also, a highpowered computer to support the work of professionals in engineering, science, and other areas that require extensive computing power and graphics capabilities.
V. DISCUSSION QUESTIONS
Do you agree with the statement: “The network is the computer”?
What trends are occurring in the development and use of the major types of computer systems?
Do you think that network computers (NCs) will replace personal computers (PCs) in business applications?
Are networks of PCs and servers making mainframe computers obsolete?
What trends are occurring in the development and use of peripheral devices? Why are those trends occurring?
When would you recommend the use of each of the following:
Information appliances in business applications
What processor, memory, magnetic disk storage, and video display capabilities would you require for a personal computer that you would use for business purposes?
What other peripheral devices and capabilities would you want to have for your business PC?