Transcript Review the ppt notes

Review For Final
(Fall 2012)
© Abdou Illia
1
Computer Hardware
2
The Core Computer Components

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

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
4
Printers

Speed and resolution


Pages per minute (PPM)
Dots per inch (DPI)



Impact printers



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

Create image by spraying or rolling ink on the page
5
I/O or Secondary Storage devices

Secondary compared to the main primary memory called RAM
Nonvolatile1 storage of digital data - Could be Magnetic, Optical,

Magnetic storage (data stored on magnetically coated surface)




Examples: Magnetic tape, Hard disk, floppy disk
Sequential access (e.g. tape) or direct access (e.g. HDD)
HDDs are electromechanical devices with spinning disks and
movable disks




Use standards/interfaces like
• 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) or GBps
• Average Read Time (in milliseconds or ms)
• Platter rotation speed in RPM (5400/7200/10,000/15,000)
State Solid Disks (SSD)



use microchips which retain data in non-volatile memory chips
No moving parts | Have lower access time and latency
256GB Crucial m4 2.5-inch
Can replace your existing HDD if same interface
SATA 6GB/s
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
Motherboard: chipset that all components connect to
 Two major components in processing subsys.



CPU (Central Processing Unit) or Processor(s)
Primary Storage:
 Random Access Memory (RAM)
 Read Only Memory (ROM)
Other
components
on the
Motherboard
CPU
Busses that
transfer data
Primary Storage
8
Central Processing Unit
Processor

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
Clock
Instruction
Control Unit
Arithmetic
Logic Unit
Registers
9
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
Speed is also measured in FLOPS* …

especially in fields of scientific calculations where long
divisions called Floating point divisions are used.
Intel
-
Major Processor manufacturers
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
*FLoating point Operations Per Second
10
Primary Storage
 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)
Primary Storage
RAM
Program

RAM holds running programs
and the data they use

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

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

Physical media



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)

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
16
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)

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

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)
18
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

19
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

20
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
21
Network Architecture

Defines how the
processing takes
place on the network

Two primary types


Client-server
Peer-to-peer (P2P)
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 P2P networks
23
The Internet and
eBusiness
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 eBay
2002 Denial of service attack knocks out 8/15 root DNS
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servers
Accessing the Internet (www)
Web
Browser
Network
Packet
Webserver
Software
Packet
Route
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. 128.150.50.9)
Webserver needs:
- Network (or Server) Operating System
- TCP/IP
- Domain name (e.g. eiu.edu)
- Internet access
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- IP Address (e.g. 139.67.8.3)
Internet applications/services
 E-Mail
 File
transfers
 Instant messaging (IM)
 Newsgroups
 Streaming audio and video
 Internet telephony or VoIP
 World Wide Web (WWW)
 Portal
27
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 28
Virtual Private Network (VPN)
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
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 notes posted to
Notes’ section of website
Notes
9,14,
7
5-6
18,19
30
Managing Security
31
Best way to prepare

Review the ppt notes or corresponding
chapter in the book to make sure you can
answer the following questions

Security Questions available in the Review section
of course web site
32
Managing the Development
and Purchase of IS
33
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
34
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
35
Traditional Systems Development
Planning
Life Cycle (SDLC)
Analysis

Seven phases
1)
2)
3)
4)
Planning
Systems Analysis
Systems Design
Development
Design
5) Testing
6) Implementation
7) Maintenance
Development
Testing
Implementation

Typically one phase needs to be
completed before beginning the next

Problem in later phase may require
return to previous phase
Maintenance
36
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
37
Feasibility Analyses
Planning

Feasibility analyses

Technical 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



Do the technologies exist to develop the system?
Economic Analysis


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
38
Project Management software
Systems Analysis
Analyze current system
Define new system requirement

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
39
Systems Analysis

Analyze current system
Define new system requirements
Step 2: Define new system’s requirements

Main Objective:


To be defined:





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

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
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

Using the requirements from Systems Analysis phase
to design the new or modified system.

Logical systems design




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



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
Scope creep
Feature creep
Performed by system designer or (system analyst in
42
some case)
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)
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

Programmers test modules



Development team do unit testing


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)


Verification: Testing system in simulated
environment with simulated data
Validation: Testing system in real working
environment with real data
45
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
46
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
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
TCO, Project Management
software
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
5. Testing
Development team, Users
Verification, Validation
6. Implementation
Development team, Users
Direct cutover, parallel conversion,
pilot testing, staged conversion
7. Maintenance
internal IS staff, external
consultant
programming languages
Make sure you can answer questions about System
Development (see SDM Quest link in Review section)
49
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

50
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
51
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.
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

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.
54
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.
55
Joint Application Development (JAD)
Identify a valid
sample of users
Objectives
Set a JAD team
(Users, IS professionals, scribe)
Run the 1st JAD session
(JAD team + Facilitator)
Identify agreed upon systems requirements
Develop system prototype
(based on agreed requirements)
Run the 2nd JAD session
(JAD team + Facilitator)
Test the system and identify agreed changes
Improve system prototype
(based on JAD session results)
56
Question 2

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)

Advantages:



Helps alleviate conflicting requirements
Its gGreater users involvement leads to
greater user acceptance of final system
Disadvantages

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
 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
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 1st
JAD session? What is the main problem associated with
JAD?
4) What is RAD? What is an ICASE tool
61