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Chapter 3

Uma GuptaIntroduction to Information Systems

Computer Hardware

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Learning Objectives

After studying this chapter, you will be able to:

Discuss the fundamentals of data representation Describe the five hardware components in a

computer system and their main functions Compare and contrast different types of computers

according to size and speed: supercomputers, mainframes, minicomputers, workstations, and microcomputers

Explain the process of buying a personal computer

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Size and Time Units for Computers

Amount of MemoryUnit

Byte

Kilobyte (kB)

Megabyte (MB)

Gigabyte (GB)

Terrabyte

8 bits

1,000 (103) bytes*

1,000,000 (106) bytes

1,000,000,000 (109) bytes

1,000,000,000,000 (1012) bytes

* This number is an approximation. The exact value is 1,024 bytes.

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The Five Computer Components

The central processor

Secondary storage

Input devices

Output devices

Communication devices

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The Central Processor

The central processor consists of two parts The central processing unit (CPU)

– Arithmetic-log unit (ALU)

– The control unit

Primary storage– Random access memory (RAM)

– Read-only memory (ROM)

– Cache memory

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Secondary Storage

There are two main types of secondary storage Sequential

– Magnetic tape

Direct access– Magnetic disks

– Redundant array of independent disks (RAID)

– CD-ROM

– Digital Versatile Disk (DVD)

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Input Devices

Input devices are the devices through which a computer accepts data Touch screens Voice-recognition systems Optical character reader (OCR)

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Output Devices

An output device is any device that helps the user to view the output of the computer Computer screen (video display terminal) Printers

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Features of the Three Types of Printers

FeaturesType of Printer

Dot Matrix Cheapest type of printer. Uses pins to press on a ribbon to make characters. Noisiest type of printer.

Higher-quality output than the dot matrix. Uses a nozzle to spray ink onto a page. Produces about 2 to 8 ppm. Can print documents in color. Quieter than a dot matrix printer, but more expensive to operate.

Highest-quality output, comparable to magazine output. Quietest printer. Typically the most expensive printer. Produces 4 to 16 ppm or more.

Inkjet

Laser

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Communication Devices

Devices that allow users separated by distance and time to exchange documents, files, graphics, and other digital information.

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Computers That Support Different Work-group Sizes

Personal InformationSystems

Work-group SystemsEnterprise-wide Systems

• PCs• Laptops/Notebooks• Hand-held Computers• Pen-based Computers

• Midrange orMinicomputers

• Workstations

• Supercomputers• Mainframes

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Supercomputers

Some of the fastest and largest computers available today are supercomputers

Supercomputers have two common characteristics The ability to process instructions in parallel

(parallel processing) The ability to automatically recover from

failures (fault tolerance)

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Mainframes

Mainframes are frequently enterprise-wide systems and are ideal for transaction processing, financial applications, payroll, investment analysis, and other applications that require extensive computations

Many users can simultaneously use the mainframe

One large disadvantage of the mainframe is that it is expensive to purchase, operate, and maintain

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Midrange,or Minicomputers, and Workstations

Although midrange computers are slower and often have less memory than mainframes, they are workhorses that can deliver excellent “bang for the buck”

Workstations lie somewhere between midrange and personal computers They can be used by individuals or groups They are faster and more sophisticated than PCs They include numerous productivity tools that

increase efficiency

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Network Computers

The network computer, also known as “thin clients” is a simplified version of a personal computer They are used mainly to access programs that reside on a

company’s network or on the Internet

Network computers are well suited for task-oriented jobs, such as data entry, order entry, and assembly line work

Network computers function by downloading all applications from a central computer and obtaining and storing all data back on the central computer

Network computers can offer cost efficiencies, but they rely heavily on network traffic and can cause bottlenecks

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Microcomputers or Personal Computers (PCs)

The memory size and processing capabilities of microcomputers are less than mainframes and midrange computers

However, hardware technology advances have made the PC a compact and powerful machine

A PC can be configured to meet the specific needs of users

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Mobile Computers: Laptops, Notebooks, Handheld, and Pen-based

These computers are battery operated so they can be used anytime, anywhere

The portability of notebook and handheld computers has increased the productivity of many employees

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A Comparison of Types of Mobile Computers

DescriptionType

Laptop Fits on a user’s lap and is slightly larger than a notebook. Has full PC functionality with a reduced keypad and screen. Has a floppy drive.

Has full PC functionality with a reduced keypad and screen and no floppy drive.

Smaller than a laptop or notebook computer. Has a built-in monitor that can be operated from the palm of one’s hand so the keyboard and screen are smaller than a laptop. Often, the keyboard requires an electronic pen to input data.

Uses an electronic writing pad and a light-sensitive electronic pen to input data.

Can download text, photos, and other applications from PCs and transmit data via infrared rays; users input information on the LCD watch face that turns into a small keyboard.

Notebook

Handheld

Pen-based

Wrist

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Six Technical Considerations in Buying a PC

Monitors

RAM

SecondaryStorage

ClockSpeed

Processor

ExpansionSlots

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Business Guidelines for Hardware Success

Cost Is Only Part of the Story Many benefits resulting from information systems

are intangible and tough to measure– increased productivity– improved decision making– faster customer service

Don’t Compromise on Capacity and Reliability The motto “If it ain’t broke, don’t fix it” does not

apply to hardware capacity and reliability

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Business Guidelines for Hardware Success (cont.)

Infrastructure, Infrastructure, Infrastructure Machines no longer work in isolation All business decisions should consider the technology

infrastructure and IS professionals should be prepared to sell its importance to top management

Support Is Crucial When there is a problem, users expect the problem to

be fixed almost immediately Who will provide support? What is the nature of

support? When will the support be provided?