Review For Final Fall 2010 Abdou Illia 1

Review For Final (Fall 2010) © Abdou Illia 1

Computer Hardware 2

The Core Computer Components p Four subsystems in a computer system: 1. Input subsystem 2. Processing subsystem 3. Output subsystem 4. I/O (Storage) subsystem Input/Output (storage) Input Process Output 3

Output Devices p Monitors n n n Cathode ray tube (CRTs) Liquid crystal displays (LCDs) Quality of display p p Resolution in pixels (e. g. 640 x 480) Dot pitch in millimeters (. 26 to. 28) Active-Matrix vs. Passive-Matrix display Touch screens n 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 4

Printers p Speed and resolution n n Pages per minute (PPM) Dots per inch (DPI) p p p Impact printers n n p Number of ink dots to fill a square inch Higher DPI = greater page clarity Create image by striking paper and ribbon Dot-matrix printers = most common impact printers Non-impact printers n Create image by spraying or rolling ink on the page 5

I/O or Secondary Storage devices p Secondary compared to the main primary memory called RAM Nonvolatile 1 storage of digital data Could be Magnetic or Optical p Magnetic storage (i. e. data stored on magnetically coated p p surface) n n n Examples: Magnetic tape, Hard disk, floppy disk Sequential access (e. g. tape) or direct access (e. g. HDD) Hard disks p many standards: § Parallel ATA (PATA) or IDE (Integrated Drive Electronics) § Serial ATA (SATA)2 § SCSI (Small Computer System Interface) p p 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 shortage 2. In SATA and PATA, ATA stands for Advanced Technology Attachment 6

Measuring Storage Capacity 7

Processing subsystem p Two major components CPU (Central Processing Unit) or Processor(s) p Primary Storage: p § Random Access Memory (RAM) § Read Only Memory (ROM) CPU Busses that transfer data Primary Storage 8

Central Processing Unit Processor p Clock: generate time that synchronize other components p ICU: Fetches instructions from RAM p ALU: Execute instructions (arithmetic & logic operations) p Registers: Store control information, data, intermediate results Clock Instruction Control Unit Registers Arithmetic Logic Unit 9

CPU speed p Speed measured in hertz n n n Hertz = # of instructions executed per second Megahertz = 1 million of instructions per second Gigahertz = 1 billion of instructions per second Major Processor manufacturers Intel - Celeron - Pentium 3, Pentium 4 Xeon, Dual Core Advanced Micro Devices (AMD) - K 6 series processors (which compete with Intel Pentium 3) - Athlon series (which compete with Intel Pentium 4) IBM - Power. PC 740, 750 FX, 750 GL, 750 GX 10

Primary Storage p Computer’s memory stored on semiconductor chips p Two categories: p RAM (Random Access Memory) which is volatile § Synchronous Dynamic RAM (SDRAM) § Double Data Rate SDRAM or DDR SDRAM p ROM (Read-Only Memory) which is non-volatile p Capacity in Megabytes (MB) or Gigabytes (GB) Primary Storage RAM Program p RAM holds running programs and the data they use p ROM contains critical programs such as those that boot the computer Data ROM 11

Summary Questions Book 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? 12

Network Technology 13

Computer Network p Once connected to the network, the computer (or another device) becomes a network node An interconnection of computers and computing equipment using either wires or radio waves over small or large geographic distances GHI DEF ABC MNO “Connect to GHI” JKL 14

Physical Transmission Media p Physical media n n n Wireless Transmission media used to physically connect nodes in to the network Transmits electrical or optical signals Could be cooper wire or fiber optic cable 15

Transmission Media (Continued) p Twisted Pair Category Use Signal Data rate Distance Problem Category 1 Telephone Analog/Digital <100 Kbps 3 -4 miles Security, noise Category 2 T 1, 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 16

Wireless Media p p p Uses electromagnetic waves or electromagnetic radiation for data transmission Propagation through space, and indirectly, through solid objects Two kinds of wireless media used n Radio waves (radio Frequency) n Infrared light § § Affected by Multipath interference Highly vulnerable to snooping Limited distance Blocked by thick objects § Close proximity and “line of sight” location required Laptop Comm. Tower 17

Network Topologies p The configurations of network components n n p How physically the network looks like How logically data is transferred on the network Widely used network topologies: n n Bus Star Ring (Mesh, not common in business setting) 18

Bus Network Topology Most simple network topology p All devices connected to a common central cable called a “bus” p Inexpensive p If cable fails, the entire network will shut down p 19

Star Network Topology Centered around central device called a hub or a switch p All network nodes connect to the hub/switch p Easy to install and update p If hub fails, network fails p 20

Ring Topology p Node connected to a logical ring in a central device called MAU p More reliable than bus or star n p Only one node sends at a time (no collisions) Expensive and limited speed 21

Network Architecture p Defines how the processing takes place on the network p Two primary types n n Client-server Peer-to-peer (P 2 P) 22

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 P 2 P networks 23

The Internet and e. Business 24

Brief history of the Internet Make sure you know what DNS is used for. 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 e. Bay 2002 Denial of service attack knocks out 8/15 root DNS 25 servers

Accessing the Internet (www) Web Browser Network Packet Webserver Software Packet Router 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. 9) Webserver needs: - Network (or Server) Operating System - TCP/IP - Domain name (e. g. eiu. edu) - Internet access 26 - IP Address (e. g. 139. 67. 8. 3)

Internet applications/services p E-Mail p File transfers p Instant messaging (IM) p Newsgroups p Streaming audio and video p Internet telephony or Vo. IP p World Wide Web (WWW) p Portal 27

Intranets and Extranets p Intranet n n Internal company network that uses Internet and WWW technologies. Typical Use: Finding and sharing work documents p Collaboration between employees to work in teams p Communication tool p n p Typically, only internal employees can get access Extranet n n n 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) 28

Portal p Portal n Web site that offers a broad array of resources and services; such as email p newsgroup p Serach engines p Online shopping malls p n Example: yahoo!, msn, aol 29

Summary Questions Book 1) (a) Name some Internet applications/services (b) What is Instant Messaging? 2) (a) What does a user PC needs for accessing the World Wide Web? (b) What is needed on the webserver side? 3) Name some Internet connection options available for residential users and businesses. 4) (a) What is an intranet? (b) an extranet? Refers to the slide # in class posted notes Notes 9, 14, 7 5 -6 18, 19 30

Managing Security 31

Best way to prepare p Review the ppt notes or chapter 4 in the book to make sure you can answer the following questions n Chapter 4 Review Questions available in the Review section of course web site 32

Managing the Development and Purchase of IS 33

Systems Development Methodology? p The process companies go through to develop and maintain an information system p Framework for successful IS development p A System Development Methodology is used p n For building a new system n Or for modifying an existing system Examples of SDM: n System Development Life Cycle ￭ Prototyping n Joint Application Development ￭ Rapid Application Development 34

Questions p 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 35

Traditional Systems Development Planning Life Cycle (SDLC) Analysis p Seven phases 1) 2) 3) 4) Planning Systems Analysis Systems Design Development Design 5) Testing 6) Implementation 7) Maintenance Development Testing Implementation p Typically one phase needs to be completed before beginning the next p Problem in later phase may require return to previous phase Maintenance 36

Question p 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 q True q False 37

Feasibility Analyses Planning p Feasibility analyses n Technical Analysis p n Can the organization afford the system? Will it provide an adequate Benefit? Operational Analysis (i. e. assessing the human element of the proposed system) p p Resistance to change Organizational politics System development schedule n n p Do the technologies exist to develop the system? Economic Analysis p p System Development Schedule Is the proposed development time line realistic? Is the programming team available during Programming step? Planning performed by Project Manager using n n n Search and investigation (e. g. for technical analysis step) Total Cost of Ownership analysis 38 Project Management software

Systems Analysis Analyze current system Define new system requirement p Systems analyst works with company to understand the problem fully and to detail the requirements of the proposed system p Step 1: Analyze current system n Objectives: p p n Understand what things are done and how (business processes) Identify any problems associated w/ current business processes Techniques: p p p Observe employees at work Talk to employees (potential users) Conducting interviews 39

Systems Analysis p Analyze current system Define new system requirements Step 2: Define new system’s requirements n Main Objective: p n To be defined: p p n Specify What need to be done (not how to do it) Input requirements (nature of data, source, etc. ) Processing requirements Output requirements (Types of reports, content, etc. ) Storage requirements Tools and techniques p Data flow diagrams (DFD) § Start with high level process § Add more levels with increased levels of detail p Computer-Aided Software Engineering (CASE) tools § Software that eases the systems development process 40

Data Flow Diagrams (DFD) 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 Data flow . Symbolized by an arrow. . Shows data being passed from or to a process External Entity 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. Data storage Used to store data in the system. Represents a file, a database, etc. 41

Systems Design p Using the requirements from Systems Analysis phase to design the new or modified system. n Logical systems design p p p n 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 p p p Uses System flowcharts to show relationships between modules Physical systems design p n Details the system’s functionality (what it should do? ) Uses Structure charts to create top-down representation of system’s modules Scope creep Feature creep Performed by system designer or (system analyst in 42 some case)

Development p p p 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) 2) 3) 4) 5) Review the input, processing, output, and storage requirements Develop the logic of the programs (using Flowcharts and Pseudo code) Write the programs using code generators & programming languages Test and debug the programs Complete the programs documentation 43

Development tools Program Flowchart: Graphical illustration of the problem-solving logic within a program Pseudocode: English-language statements that describe the processing steps of a program in paragraph form. Code generators: Software that generate programs that programmers could modify. Programming languages: -Java -C++ -Visual Basic -Etc. 44

Testing p Programmers test modules p p p Development team do unit testing p p Do they return proper outputs? Do they handle incorrect data appropriately? i. e. testing how modules work together System testing (software along with database and network component) n n Verification: Testing system in simulated environment with simulated data Validation: Testing system in real working environment with real data 45

Implementation p p Implementation strategies n Direct cutover: Quick change to new system n Parallel conversion: Old and new systems used in parallel for a while. n Pilot testing: New system installed at only one location or one department n Staged conversion: Only one part of the system installed, then another part is installed. User training 46

Maintenance counts for as much as 80% of the total cost of an information system p Tasks p n n Correct errors found during implementation System enhancements Incremental upgrades p Addition of major new features p 47

Summary Questions Book 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? 48

SDLC: Recap Steps 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) 49

Problems with Traditional SDLC is time consuming p SDLC is not flexible (sequential process) p SDLC gets users’ inputs ONLY during Systems analysis. p Design is frozen at end of System Design p 50

Question 1 p 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 51

Prototyping p. A n n SDM that addresses: Time consuming issue associated with SDLC’s inability to take care of new requirements p. 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. 52

Prototyping Actors Identify basic requirements Operational prototype YES Development team, Users Develop a prototype System analyst, programmer Use the prototype Users Is User satisfied? NO Develop final system (improved prototype) Revise the prototype System analyst, programmer 53

Prototyping p Advantages n n n p Working model ready quickly Works in situation where requirements are changing Works in situations where users cannot explicitly express their requirements Disadvantage n Only a limited number of users involved. So, subject to potential implementation problem. 54

Joint Application Development (JAD) p. A n n SDM that addresses: The limited scale of users involvement problem of Prototyping Potential implementation problem due to limited users involvement p. A SDM that brings together the Development team and a significant number of users to define system requirements and develop a prototype. 55

Joint Application Development (JAD) Identify a valid sample of users Objectives Set a JAD team (Users, IS professionals, scribe) Run the 1 st JAD session (JAD team + Facilitator) Identify agreed upon systems requirements Develop system prototype (based on agreed requirements) Run the 2 nd JAD session (JAD team + Facilitator) Test the system and identify agreed changes Improve system prototype (based on JAD session results) 56

Question 2 p Which of the following is true about a JAD facilitator? (Choose all that apply) a) Could be an outside consultant b) Is the scribe who takes notes c) Is responsible for coordinating the JAD sessions d) Is responsible for developing the system based on the agreed upon requirements e) All of the above 57

Joint Application Development (JAD) p Advantages: n n p Helps alleviate conflicting requirements Its g. Greater users involvement leads to greater user acceptance of final system Disadvantages n Could be expensive and time consuming 58

Rapid Application Development (RAD) Combines JAD, Prototyping, and use of Integrated CASE (ICASE) tools to decrease the time for systems development p ICASE tools provide code generating capability p n n ICASE tools can produce a completed program based on the diagrams developed by systems analysts ICASE tools can generate tables for a databased on detailed system specifications 59

Rapid Application Development (RAD) Typical use of RAD Define requirements through JAD session Use ICASE to produce DFD and detailed Data storages’ specifications Use ICASE to generate tables for Data storages Use ICASE to generate programs 60

Summary Questions Malaga 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 1 st JAD session? What is the main problem associated with JAD? 4) What is RAD? What is an ICASE tool 61