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Review For Final

© Abdou Illia

(Fall 2010)

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Computer Hardware

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The Core Computer Components

Four subsystems in a computer system:1. Input subsystem 3. Output subsystem2. Processing subsystem 4. I/O (Storage) subsystem

InputProcess

Output

Input/Output (storage)

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Output Devices Monitors

Cathode ray tube (CRTs) Liquid crystal displays (LCDs) Quality of display

Resolution in pixels (e.g. 640 x 480) Dot pitch in millimeters (.26 to .28) Active-Matrix vs. Passive-Matrix display

Touch screens Input and output via display device

Monitor size Common resolution

15 inches 640 x 480

17 inches 800 x 600 or 1024 x 768

19 inches 1024 x 768 or 1280 x 1024

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Printers Speed and resolution

Pages per minute (PPM) Dots per inch (DPI)

Number of ink dots to fill a square inch Higher DPI = greater page clarity

Impact printers Create image by striking paper and ribbon Dot-matrix printers = most common impact printers

Non-impact printers Create image by spraying or rolling ink on the page

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I/O or Secondary Storage devices

Secondary compared to the main primary memory called RAM Nonvolatile1 storage of digital data Could be Magnetic or Optical Magnetic storage (i.e. data stored on magnetically coated

surface) Examples: Magnetic tape, Hard disk, floppy disk Sequential access (e.g. tape) or direct access (e.g. HDD) Hard disk disks

many standards: Parallel ATA (PATA) or IDE (Integrated Drive Electronics) Serial ATA (SATA)2

SCSI (Small Computer System Interface) SCSI provides disk fault-tolerance by using RAID – Redundant Array of

Inexpensive Disks; that is multiple disks set together to provide continued service in case one disk fails.

Disk speed: Transfer rate in MBps (Megabytes per second) Average Read Time (in milliseconds or ms) Platter rotation speed in RPM (5400/7200/10,000/15,000)

1. Means that the stored data wouldn’t disappear (or be deleted) in case of power shortage2. In SATA and PATA, ATA stands for Advanced Technology Attachment

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Measuring Storage Capacity

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Processing subsystem Two major components

CPU (Central Processing Unit) or Processor(s) Primary Storage:

Random Access Memory (RAM) Read Only Memory (ROM)

CPU

Primary Storage

Busses that transfer data

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Central Processing Unit

Clock: generate time that synchronize other components

ICU: Fetches instructions from RAM

ALU: Execute instructions (arithmetic & logic operations)

Registers: Store control information, data, intermediate results

Processor

Clock

Instruction Control Unit

Arithmetic Logic Unit

Registers

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CPU speed Speed measured in hertz

Hertz = # of instructions executed per second Megahertz = 1 million of instructions per second Gigahertz = 1 billion of instructions per second

Intel- Celeron

- Pentium 3, Pentium 4, Pentium 4 Xeon, Dual Core

Advanced Micro Devices (AMD)

- K6 series processors (which compete with Intel Pentium 3)

- Athlon series (which compete with Intel Pentium 4)

IBM

- PowerPC 740, 750, 750FX, 750GL, 750GX

Major Processor manufacturers

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Primary Storage

RAM holds running programs and the data they use

ROM contains critical programs such as those that boot the computer

Primary Storage

RAM

ROM

Computer’s memory stored on semiconductor chips Two categories:

RAM (Random Access Memory) which is volatile Synchronous Dynamic RAM (SDRAM) Double Data Rate SDRAM or DDR SDRAM

ROM (Read-Only Memory) which is non-volatile

Capacity in Megabytes (MB) or Gigabytes (GB)

Program Data

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Summary QuestionsBook Notes

1) Name two devices that could be used for both input and output.

2) What is the difference between: (a) a Kilobyte and a Gigabyte? (b) a Megabyte and a byte?

3) What is the function of the Instruction Control Unit or ICU found in the processing subsystem?

4) Explain the difference between RAM and ROM.

5) What is pixel? What is dot pitch

6) What is a byte?

7) What is a Hertz?

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Network Technology

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Computer Network An interconnection of computers and

computing equipment using either wires or radio waves over small or large geographic distances

“Connect to GHI”ABC

DEF GHI

JKLMNO

Once connected to the network, the computer (or another device) becomes a network node

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Transmission Media Physical media

Transmission media used to physically connect nodes in to the network

Transmits electrical or optical signals Could be cooper wire or fiber optic cable

Physical

Wireless

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Transmission Media (Continued) Twisted Pair

Category Use Signal Data rate Distance Problem

Category 1 Telephone Analog/Digital <100Kbps 3-4 miles Security, noise

Category 2 T1, ISDN Digital <2 Mbps 3-4 miles Security, noise

Category 3 LANs Digital 10 Mbps 100 m Security, noise

Category 4 LANs Digital 20 Mbps 100 m Security, noise

Category 5 LANs Digital 100 Mhz 100 m Security, noise

Category 6 LANs Digital 250 Mhz 100 m Security, noise

Category 7 LANs Digital 600 Mhz 100 m Security, noise

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Wireless Media Uses electromagnetic waves or electromagnetic radiation for

data transmission Propagation through space, and indirectly, through solid objects Two kinds of wireless media used

Radio waves (radio Frequency) Affected by Multipath interference Highly vulnerable to snooping Limited distance Blocked by thick objects

Infrared light Close proximity and “line of sight” location required

LaptopComm. Tower

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Network Topologies The configurations of network components

How physically the network looks like How logically data is transferred on the network

Widely used network topologies: Bus Star Ring (Mesh, not common in business setting)

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Bus Network Topology Most simple network topology All devices connected to a common central

cable called a “bus” Inexpensive If cable fails, the entire network will shut

down

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Star Network Topology Centered around

central device called a hub or a switch

All network nodes connect to the hub/switch

Easy to install and update

If hub fails, network fails

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Ring Topology

Node connected to a logical ring in a central device called MAU

More reliable than bus or star Only one node sends at a

time (no collisions)

Expensive and limited speed

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Network Architecture

Defines how the processing takes place on the network

Two primary types Client-server Peer-to-peer (P2P)

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Summary Questions

Malaga Notes

1) What is a node?

2) Name physical and wireless media used in networking

3) What transmission media is used for the telephone?

4) What are the main network topology? What are the differences between them?

5) Distinguish between Client-server and P2P networks

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The Internet and eBusiness

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Brief history of the Internet

1969 The Defense Advanced Research Projects developed ARPANET, the precursor of the Internet

1971 Ray Tomlison invents e-mail

1979 USENET newsgroups created at Duke University and the University of North Carolina

1984 Domain Name System (DNS) established

1991 Tim Berners-Lee creates the World Wide Web

1994 First online shopping mall, first spam email, first pizza ordered online, first advertisement banner

2000 A major denial of service attack brings down websites such as Yahoo!, Amazon.com, and eBay

2002 Denial of service attack knocks out 8/15 root DNS servers

Make sure you know what DNS is used for.

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Webserver needs:- Network (or Server) Operating System- TCP/IP- Domain name (e.g. eiu.edu)- Internet access - IP Address (e.g. 139.67.8.3)

User PC needs:- Workstation Operating System- TCP/IP- Web browser (e.g. Internet Explorer)- Internet access (e.g. thru an ISP)- IP Address (e.g. 128.150.50.9)

Accessing the Internet (www)

NetworkWeb

Browser

Packet

Router

Packet

Route

WebserverSoftware

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Internet applications/services E-Mail File transfers Instant messaging (IM) Newsgroups Streaming audio and video Internet telephony or VoIP World Wide Web (WWW) Portal

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Intranets and Extranets Intranet

Internal company network that uses Internet and WWW technologies.

Typical Use: Finding and sharing work documents Collaboration between employees to work in teams Communication tool

Typically, only internal employees can get access

Extranet Web site that allows customers and business

partners limited access to organizational intranet Uses Internet and WWW technologies Add additional security through the use of a

Virtual Private Network (VPN)

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Portal Portal

Web site that offers a broad array of resources and services; such as

email newsgroup Serach engines Online shopping malls

Example: yahoo!, msn, aol

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Summary Questions

Refers to the slide # in class posted notes

Book Notes

1) (a) Name some Internet applications/services (b) What is Instant Messaging?

9,14,

2) (a) What does a user PC needs for accessing the World Wide Web? (b) What is needed on the webserver side?

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3) Name some Internet connection options available for residential users and businesses.

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4) (a) What is an intranet? (b) an extranet? 18,19

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Managing Security

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Best way to prepare Review the ppt notes or chapter 4 in the

book to make sure you can answer the following questions Chapter 4 Review Questions available in the

Review section of course web site

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Managing the Development and

Purchase of IS

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Systems Development Methodology? The process companies go through to

develop and maintain an information system Framework for successful IS development A System Development Methodology is used

For building a new system Or for modifying an existing system

Examples of SDM: System Development Life Cycle ￭ Prototyping Joint Application Development ￭ Rapid Application Development

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Questions Which of the following is true about SDM?

1) They provide guidelines for developing IS and maintaining them which includes upgrading and improving them.

2) SDM are needed when a brand new IS has to be developed, but you don’t need to use a SDM when it comes to modifying an existing IS.

3) When a company is engaged in developing an IS, the process involves the company’s employees who would be the future users of the IS, and IS professionals like system analysts and programmers. But it doesn’t involve the company’s management

4) All of the above

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Traditional Systems Development Life Cycle (SDLC)

Seven phases 1) Planning 5) Testing2) Systems Analysis 6) Implementation3) Systems Design 7) Maintenance4) Development

Typically one phase needs to be completed before beginning the next

Problem in later phase may require return to previous phase

Planning

Analysis

Design

Development

Testing

Implementation

Maintenance

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Question

In SDLC, the 7 phases are typically followed in a sequential order, which means we don’t return to a previous phase in any circumstances

True False

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Planning Feasibility analyses

Technical Analysis Do the technologies exist to develop the system?

Economic Analysis Can the organization afford the system? Will it provide an adequate Benefit?

Operational Analysis (i.e. assessing the human element of the proposed system)

Resistance to change Organizational politics

System development schedule Is the proposed development time line realistic? Is the programming team available during Programming

step? Planning performed by Project Manager using

Search and investigation (e.g. for technical analysis step) Total Cost of Ownership analysis Project Management software

Feasibility Analyses

System Development Schedule

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Systems Analysis Systems analyst works with company to understand

the problem fully and to detail the requirements of the proposed system

Step 1: Analyze current system Objectives:

Understand what things are done and how (business processes) Identify any problems associated w/ current business processes

Techniques: Observe employees at work Talk to employees (potential users) Conducting interviews

Analyze current system

Define new system requirement

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Systems Analysis Step 2: Define new system’s requirements

Main Objective: Specify What need to be done (not how to do it)

To be defined: Input requirements (nature of data, source, etc.) Processing requirements Output requirements (Types of reports, content, etc.) Storage requirements

Tools and techniques Data flow diagrams (DFD)

Start with high level process Add more levels with increased levels of detail

Computer-Aided Software Engineering (CASE) tools Software that eases the systems development process

Analyze current system

Define new system requirements

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Data Flow Diagrams (DFD)

Data flow

Process

External Entity

Data storage

. Symbolized by an arrow.

. Shows data being passed from or to a process

. Symbolized by a rectangle or a curved rectangle.

. Action performed by people of organizational units in order to transform input into output OR Action performed by people in the organizational units to help the units achieve their objectives

Symbolized by a square, an external entity is something (person, group, department, etc.) outside the system that interacts with the system by providing input or receiving information.

Used to store data in the system. Represents a file, a database, etc.

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Systems Design Using the requirements from Systems Analysis phase

to design the new or modified system. Logical systems design

Details the system’s functionality (what it should do?) Uses Structure charts to create top-down representation of

system’s modules Uses System flowcharts to show relationships between modules

Physical systems design Specifies all of the actual components (hardware, network, etc) used

to implement the logical design The design must be frozen at end of this phase to prevent the

to system grow indefinitely in terms of its scope and features Scope creep Feature creep

Performed by system designer or (system analyst in some case)

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Development Programming process is usually the most

difficult and time consuming in the Development process.

Development performed by programmers, database developers, and network engineers

Programmers use Program Development Cycle

1) Review the input, processing, output, and storage requirements2) Develop the logic of the programs (using Flowcharts and Pseudo code)3) Write the programs using code generators & programming languages4) Test and debug the programs5) Complete the programs documentation

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Development tools

Program Flowchart:

Graphical illustration of the problem-solving logic

within a programPseudocode:

English-language statements that describe the processing steps of a

program in paragraph form.

Programming languages:-Java-C++-Visual Basic-Etc.

Code generators:Software that generate programs that programmers could modify.

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Testing Programmers test modules

Do they return proper outputs? Do they handle incorrect data appropriately?

Development team do unit testing i.e. testing how modules work together

System testing (software along with database and network component)

Verification: Testing system in simulated environment with simulated data

Validation: Testing system in real working environment with real data

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Implementation Implementation strategies

Direct cutover: Quick change to new system

Parallel conversion: Old and new systems used in parallel for a while.

Pilot testing: New system installed at only one location or one department

Staged conversion: Only one part of the system installed, then another part is installed.

User training

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Maintenance Maintenance counts for as much as 80%

of the total cost of an information system Tasks

Correct errors found during implementation System enhancements

Incremental upgrades Addition of major new features

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Summary QuestionsBook Notes

1) What is a System Development Methodology? What is it used for?

2) What are the 7 phases of the SDLC methodology?

3) What kind of Feasibility analyses need to be performed during the Planning phase? Why is the system development schedule important?

4) What are the two steps in the Systems Analysis phase? What techniques and tools are used during the Systems Analysis phase?

5) What tools do programmers usually use during the Development phase?

6) What is the difference between the Verification and the Validation tests performed during systems testing?

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SDLC: RecapSteps Key actors Tools/Techniques

1. Planning Project Manager Project Management software, Total Cost Ownership analysis, etc.

2. System Analysis System Analyst, Users. Interviews, observing users at work, DFD

3. System Design System analyst (or system designer)

System Flowchart, Structure chart

4. Development Programmers, database developers, network engineers

Program Flowchart, Pseudo code, programming languages, DBMS

5. Testing Development team, Users Unit testing, verification, validation

6. Implementation Development team, Users Direct cutover, parallel conversion,pilot testing, staged conversion

7. Maintenance internal IS staff, external consultant

Make sure you can answer questions about System Development (see SDM Quest link in Review section)

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Problems with Traditional SDLC SDLC is time consuming SDLC is not flexible (sequential process) SDLC gets users’ inputs ONLY during

Systems analysis. Design is frozen at end of System Design

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Question 1 Which of the following is true about SDLC?

a) It might take years to develop and implement a working information system

b) Multiple teams could work simultaneously on different phases

c) It is the best methodology for situations where the needs and requirements are likely to change during the development process

d) All of the above

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Prototyping A SDM that addresses:

Time consuming issue associated with SDLC SDLC’s inability to take care of new requirements

A SDM in which the Development team uses limited set of users requirements to quickly build a working model of the proposed system – a prototype.

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Prototyping Actors

Development team, Users

System analyst, programmer

Users

System analyst, programmer

Identify basicrequirements

Develop aprototype

Is Usersatisfied?

Use theprototype

Revise theprototype

Operationalprototype

Develop final system(improved prototype)

YES

NO

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Prototyping Advantages

Working model ready quickly Works in situation where requirements are

changing Works in situations where users cannot

explicitly express their requirements Disadvantage

Only a limited number of users involved. So, subject to potential implementation problem.

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Joint Application Development (JAD)

A SDM that addresses: The limited scale of users involvement problem of Prototyping Potential implementation problem due to limited users involvement

A SDM that brings together the Development team and a significant number of users to define system requirements and develop a prototype.

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Joint Application Development (JAD)

Identify a validsample of users

Set a JAD team(Users, IS professionals, scribe)

Run the 1st JAD session(JAD team + Facilitator)

Develop system prototype(based on agreed requirements)

Run the 2nd JAD session(JAD team + Facilitator)

Improve system prototype(based on JAD session results)

Objectives

Identify agreed upon systems requirements

Test the system and identify agreed changes

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Question 2 Which of the following is true about a JAD

facilitator? (Choose all that apply)a) Could be an outside consultantb) Is the scribe who takes notesc) Is responsible for coordinating the JAD

sessionsd) Is responsible for developing the system

based on the agreed upon requirementse) All of the above

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Joint Application Development (JAD) Advantages:

Helps alleviate conflicting requirements Its gGreater users involvement leads to greater

user acceptance of final system Disadvantages

Could be expensive and time consuming

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Rapid Application Development (RAD) Combines JAD, Prototyping, and use of

Integrated CASE (ICASE) tools to decrease the time for systems development

ICASE tools provide code generating capability ICASE tools can produce a completed program

based on the diagrams developed by systems analysts

ICASE tools can generate tables for a database based on detailed system specifications

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Rapid Application Development (RAD)

Define requirementsthrough JAD session

Use ICASE to produceDFD and detailed Datastorages’ specifications

Use ICASE to generateprograms

Use ICASE to generatetables for Data storages

Typical use of RAD

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Summary QuestionsMalaga Notes

1) What are the main problems associated with SDLC?

2) What is Prototyping? What are the steps of Prototyping? In what kind of situations Prototyping might be the best SDM to use?

3) What is JAD? Typically, who could be a member of a JAD team? Usually, what is the main objective of the 1st JAD session? What is the main problem associated with JAD?

4) What is RAD? What is an ICASE tool