Hardware: Input, Processing, and Output Devices

Hardware:

Input, Processing, and Output Devices

Chapter 3

Computer System

Special subsystem of an organization's overall information system

Integrated assembly of physical devices, centered around at least one processing mechanism utilizing digital electronics

Used to input, process, store, and output data and information

Computer System Components

[Figure 3.1]

Computer system hardware components include devices that perform the functions of input, processing, data storage, and output.

Central Processing Unit (CPU)

Arithmetic/logic unit (ALU)Performs mathematical calculationsMakes logical comparisons

Control unitSequentially accesses and decodes program instructionsCoordinates flow of data in and out of the ALU, registers, primary

storage, secondary storage, output devices

Registers High-speed storage areasTemporarily hold small units of program instructions and data

immediately before, during, and after execution by CPU

Primary Storage

Holds program instructions and data immediately before or immediately after the registers

Also called memory or main memory

Closely associated with the CPU

Execution of an Instruction

Instruction phaseStep 1: Fetch instructionStep 2: Decode instruction

Instruction time (I-time): The time to complete the instruction phase


Execution phaseStep 3: Execute instructionStep 4: Store results

Execution time (E-time): The time to complete the execution phase


Fig 3.2

CPU Characteristics

Machine cycle timeClock speedWordlength and bus line widthPhysical characteristicsComplex and reduced instruction set computing

Machine Cycle Time

Measured in fractions of a secondMillisecond - one thousandth of one secondMicrosecond - one millionth of one secondNanosecond - one billionth of one secondPicosecond - one trillionth of one second

Or in terms of instructions per second MIPS - millions of instructions per second

Clock Speed

Predetermined rate at which the CPU produces a series of electronic pulses

MicrocodePredetermined internal instructions executed in

accordance with clock speed

Often measured in megahertz (MHz) or millions of cycles per second; ranges from 20 MHz to over 200 MHz for PCs

Clock Speed and the Execution of Microcode Instructions

[Figure 3.3]

Wordlengthand Bus Line Width

BitA binary digit: 0 or 1

Wordlength Number of bits the CPU can process at any one time

Bus lines Physical wiring that connects computer system

components

Physical Characteristicsof the CPU

Moore’s Law: The hypothesis that transistor densities on a single chip will double every 18 months

[Figure 3.4]

CISC and RISC

Complex instruction set computing (CISC)Places as many microcode instructions into the central

processor as possible

Reduced instruction set computing (RISC)Reduces the number of microcode instructions built into a

chip to an essential set of common instructions

Memory

Storage capacityByte = eight bits

Kilo, Mega, Giga, Tera

Types of memoryRandom access memory (RAM)

Temporary and volatile

Read-only memory (ROM)Permanent and non-volatile

Cache memoryHigh-speed, quicker access than main memory

Basic Types of Memory Chips

Cache Memory

Multiprocessing

Processing that occurs using more than one processing unit

CoprocessorA processor that speeds processing by executing specific

types of instructions while the CPU works on another processing activity

Parallel Processing

Speeds processing by linking several processors to operate at the same time

Parallel Processing

Shared memory processing (SMP) Involves fewer processors and a common pool of main

memoryAn independent task runs on each processor

Massively parallel processing (MPP) Involves hundreds or thousands of microprocessor chips

assigned to do the computing for a single program

Parallel Processing

[Figure 3.8]

Secondary Storage

The portion of the computer that holds large amounts of data, instructions, and information more permanently than does main memory

Also called permanent storage

Cost Comparison of Various Forms of Data Storage

[Figure 3.9]

Access Method Trade-Offs

Direct accessProcess by which data and information are retrieved

directly, without the need to pass by other data in sequence

Sequential access storage device (SASD)Device used to sequentially access secondary storage

media

Access Method Trade-Offs

Direct access storage device (DASD) Device used to directly access secondary storage media

Secondary Storage Devices

Magnetic tape Common secondary storage mediaMylar film coated with iron oxide

Magnetic disksSteel platters

(hard disks) or Mylar film (floppy disks) coatedwith iron oxide

Fig. 3.11


Redundant array of independent/ inexpensive disks (RAID)Generates extra bits of data from existing data so the

system can create a “reconstruction map” to rebuild lost data

Disk mirroringProvides an exact copy of data on drive


Optical disksA rigid disk of plastic onto which data is recorded by

special lasers that physically burn pits into the disk

Compact disk read-only memory (CD-ROM) A common form of optical disk on which data, once

recorded, cannot be modified


CD-rewriteable (CD-R)Allows PC users to replace their diskettes with high

capacity CDs that can be written upon and edited over

Write-once, read-many (WORM) Allows businesses to record customized data and

information onto an optical disk


Magneto-optical disk A hybrid between magnetic disks and optical disks

Digital video disk (DVD)Looks like a CD-ROM

disk, but can store about 135 minutes of digital video

Fig. 3.12


Memory cardsCredit-card sized devices that can be installed in an

adapter or slot in many personal computers

Flash memoryA silicon chip that is nonvolatile and keeps its memory

when the power is shut off


Expandable storageStorage devices that use removable disk cartridges

Fig. 3.13


Floptical diskExperimental storage device that is the same size as a

diskette, but is able to hold many more times the data

Comparison of Secondary Storage Devices

[Table 3.2]

Speed And Functionality

The nature of dataHuman-readable data vs. machine-readable data

Data entry and inputData entry: Human-readable data is converted into a

machine-readableData input: Machine-readable data is transferred into the

system

continued...

Speed And Functionality

Source data automation Automation of data entry and input where the data is

created, thus ensuring accuracy and timeliness

Input Devices

Personal computer input devicesKeyboardMouse

Voice recognition devices

Digital computer cameras

Terminals

Scanning devices

Optical data readersOptical mark recognition

readersOptical character reader

continued...

Input Devices

Magnetic ink character recognition (MICR) devices

Point-of-sale (POS) devices

Automatic teller machine (ATM) devices

Pen input devices

Light pens

Touch-sensitive screens

Bar code scanners

Sample Input Device: Digital Computer Camera

Fig. 3.14

Sample Input Device: MICR Device

Fig. 3.15

Output Devices: Monitors

Display monitorsMonochromeRGB (red, green, blue)Color graphics adapter (CGA)Enhanced graphics adapter (EGA)Video graphics array (VGA)Extended graphics array (XGA)

Liquid crystal display (LCDs)

Output Devices: Printers, Plotters,and Microfilm

Impact printersLetter-quality printers, dot-matrix printers, near-letter

quality printers (NLQ)

Non-impact printersInk-jet printers and laser printers

Plotters Computer output microfilm devices (COM)Special-Purpose Devices: Multifunction device

A device that combines several input/output devices (e.g., printer, fax, scanner)

Classifying Computers

Special-purpose computersUsed for limited applications

General-purpose computers Most common type of computersUsed for a variety of applications

Types of Computer Systems

Personal computersNetwork computersWorkstationsMidrange computersMainframesSupercomputers

Types of Computer Systems

Personal computersRelatively small and inexpensiveAlso called microcomputers

Computer System Types

Network ComputersStripped-down personal computersPrimarily used with network system and the Internet

WorkstationsFit between high-end microcomputers and low-end

midrange computers in terms of cost and processing power

Computer System Types

Midrange computersSystems that can accommodate several users at one timeFormerly known as minicomputers

MainframesLarge powerful computers often shared by hundreds of

concurrent users connected to the machine via terminals

SupercomputersMost powerful computer systems with the fastest

processing speeds

Network Computer

Processor speed1-5 MIPs

Amount of RAM4-16 MB

Approximate cost$500-$1,500

How usedSupports data entryConnects to the Internet

ExampleOracle Network computer

Personal Computer



Approximate cost$1,200-$5,000

How usedImproves individual worker’s

productivity

ExampleCompaq Pentium computer

Workstation



Approximate cost$4,000 to over $20,000

How usedEngineering CADSoftware development

ExampleSun Microsystems computer

Midrange Computer



Approximate cost$20,00 to over $100,000

How usedMeets computing needs for a

department or small company

ExampleHewlett-Packard HP-9000

Mainframe Computer

Processor speed40-4,550 MIPs

Amount of RAM256-1,024 MB

Approximate cost$250,000 to over

$2 million

How usedMeets computing needs for a

company

ExampleIBM ES/9000

Supercomputer

Processor speed60 billion-3 trillion

instructions per sec

Amount of RAM8,192MB+

Approximate cost$2.5 million-

$3.5 million

How usedScientific applicationsMarketingCustomer supportProduct development

ExampleCray C90

Multimedia Computers

Involves the marriage of sound, animation, and digitized video

Multimedia standardsEnable software and hardware vendors to build products

that will work together to meet the needs of their customers

Multimedia Support

Microsoft multimedia extension for Windows

Multimedia PC Council (MPC)

IBM Ultimedia Solution

Multimedia Support: Audio

Musical Instrument Digital Interface (MIDI)Standard system for connecting musical instruments and

synthesizers to computers

Digital signal processor (DSP)A chip used by advanced sound systems to improved the

analog-to-digital-to-analog conversion process

Multimedia Support: Video

Video compressionA process that uses mathematical formulas to reduce the

number of bits required to present a single video frame

Hardware Components of Multimedia Computer System

[Figure 3.18]

Architecture and Upgrades: Responding to Change

Computer system architecture The structure, or configuration, of hardware components

of a computer system

Computer Standards

Approved reference models determined by groups for building various products

Common PC standards:Plug and play (PnP) Small Computer Systems Interface (SCSI)Multimedia extension (MMX)

Information Systems Principles

Assembling an efficient computer subsystem requires an understanding of its relationship to the information system and the organization. The computer system objectives are subordinate to, but supportive of, the information system and the organization.


Components of information systems (input devices, people, procedures, goals) are interdependent. Because the performance of one system affects the others, all systems should be measured according to the same standards of effectiveness and efficiency.


When selecting computer subsystem devices, consider current and future needs. The choice of a particular computer system should allow for later improvements in the overall information system. Reasoned forethought is the hallmark of a true systems professional.


Determine hardware needs based on how the hardware will be used to support the objectives of the information systems and the goals of the organization. For PC users, this means knowing what software you want to run.


Do research to gain an understanding of the trade-offs between overall system performance, and cost, control, and complexity.

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Hardware: Input, Processing, and Output Devices