Final Review

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					Computers:
Tools for an Information Age



Final Review -- Chapters 6, 10, 12, 13, 14
Secondary Storage

   Separate from the computer itself
   Software and data stored on a semi-
    permanent basis
           Unlike memory, not lost when power is lost




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Benefit: Space

   Store a roomful of data on disks smaller than
    the size of a breadbox
           Diskette contains equivalent of 500 printed pages
           Optical disk can hold equivalent of 500 books




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Benefit: Reliability

   Data in secondary storage is relatively safe
           Secondary storage is highly reliable
           More difficult for untrained people to tamper with
            data stored on disk




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Benefit: Convenience

   Authorized users can easily and quickly
    locate data stored on the computer




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Benefit: Economy

   Several factors create significant savings in
    storage costs
           Less expensive to store data on disks than to buy
            and house filing cabinets
           Reliable and safe data is less expensive to
            maintain
           Greater speed and convenience in filing and
            retrieving data



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Track

   The circular portion of the disk
    surface that passes under the
    read/write head
           Floppy diskette has 80 tracks on
            each surface
           Hard disk may have 1,000 or
            more tracks on each surface of
            each platter




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Cluster

   A fixed number of adjacent sectors that are
    treated as a unit of storage
           Typically two to eight sectors, depending on the
            operating system




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Seek Time

   The time it takes the access arm to get into
    position over a particular track
           All access arms move as a unit
           All simultaneously in position over a set of tracks
            that make up a cylinder




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Optical Disk Storage

   Provides inexpensive and compact storage with
    greater capacity
   Laser scans disk and picks up light reflections from
    disk surface
   Categorized by read/write capability
           Read-only media - user can read from, but not write to disk
           Write-once, read-many (WORM) - user can write to disk
            once
           Magneto-optical - combines magnetic and optical
            capabilities



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Compact Disks

   CD-ROM - drive can only read data from
    CDs
           CD-ROM stores up to 700 MB per disk
           Primary medium for software distribution
   CD-R - drive can write to disk once
           Disk can be read by CD-ROM or CD-R
            drive
   CD-RW - drive can erase and record over
    data multiple times
           Some compatibility problems trying to
            read CD-RW disks on CD-ROM drives



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Digital Versatile Disk (DVD)

   Short wavelength laser can read densely
    packed spots
           DVD drive can read CD-ROMs
           Capacity up to 17GB
           Allows for full-length movies
           Sound is better than on audio CDs
   Several versions of writable and rewritable
    DVDs exist


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Redundant Array of Independent Disks
(RAID)
   A group of disks that work
    together as one
           Raid level 0 spreads data from a
            single file over several drives
                Called data striping
                Increases performance
           Raid level 1 duplicates data on
            several drives
                Called disk mirroring
                Increases fault tolerance




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Organizing and Accessing Stored Data

   Character
   Field
   Record
   File
   Database




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Field

   A set of related characters
   Describes one characteristic of a person,
    place, or thing
           For a university, a student’s first name would be
            stored in a field
   Key field - a unique identifier for a record




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Record

   A collection of related fields
           For the university, all of the fields for one student
            constitute one record




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Computers:
Tools for an Information Age



Chapter 10
Security and Privacy:
Computers and the Internet
Security and Privacy

   Security – data stored on computer must be
    kept safe
   Privacy – private data must be kept from
    prying eyes




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Methods Computer Criminals Use

   Bomb                   Scavenging
   Data diddling          Trapdoor
   Denial of service      Trojan horse
    attacks                Zapping
   Piggybacking
   Salami technique




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Denial of Service Attack

   Hackers bombard a site with more requests
    than it can possibly handle
           Prevents legitimate users from accessing the site
           Hackers can cause attacks to come from many
            different sites simultaneously




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Virus

   A set of illicit instructions that
    passes itself on to other files
           Transmitting a virus
           Can cause tremendous damage
            to computer and data files
           Can be prevented
           Common computer myths




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Spamming

   Mass advertising via e-mail
           Can overflow your e-mail inbox
           Bogs down your e-mail server, increasing the cost
            of e-mail service
   Preventing spam




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Cookies

   A small text file stored on your hard drive
   File is sent back to the server each time you visit
    that site
           Stores preferences, allowing Web site to be customized
           Stores passwords, allowing you to visit multiple pages
            within the site without logging in to each one
           Tracks surfing habits, targeting you for specific types of
            advertisements




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Preventing Spam

   Many ways you can minimize junk e-mail
           Be careful how you give out your e-mail address
           Filtering software allows you to block messages or send
            them to designated folders
           Don’t register at Web sites without a promise the Web site
            will not sell your information
           NEVER respond to spam
   Anti-spamming legislation is being proposed in
    many states



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A Firewall

   A combination of hardware and
    software that sits between an
    organization’s network and the
    Internet
           All traffic between the two goes
            through the firewall
           Protects the organization from
            unauthorized access
           Can prevent internal users from
            accessing inappropriate Internet
            sites



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White-Hat Hackers

   Hackers that are paid by a company to break
    into that company’s computer systems
           Expose security holes and flaws before criminals
            find them
           Once exposed, flaws can be fixed




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Computer Forensics

   Uncovering computer-stored information suitable
    for use as evidence in courts of law
           Restores files and/or e-mail messages that someone
            has deleted
   Some experts are available for hire, but most are
    on the staffs of police departments and law firms




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A Disaster Recovery Plan

   A method of restoring computer processing
    operations and data files in the event of major
    destruction
   Several approaches
           Manual services
           Buying time at a service bureau
           Consortium
   Plan should include priorities for restoring programs,
    plans for notifying employees, and procedures for
    handling data in a different environment




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Freedom of Information Act

   Allows ordinary citizens to have access to
    data gathered about them by federal
    agencies




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Computers:
Tools for an Information Age



Chapter 12
Spreadsheets and Business Graphics:
Facts and Figures
Electronic Spreadsheets

   A computerized version of a
    paper spreadsheet
   Benefits
           Eliminates much of the
            tedium
           Calculations are error-free
           Worksheet is automatically
            recalculated when you
            change one value or
            calculation
           Performs “what-if” analysis



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Cells and Cell Addresses

   Spreadsheet is divided into rows
    and columns
   A cell is the intersection of a row
    and a column
           Cell is known by its address
                Address consists of column
                 letter, followed by row number,
                 for example B7
           Active cell - the cell available to
            be edited at a given time




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Contents of Cells

   Label – provides descriptive text information about
    entries in the spreadsheet
   Value – an actual number that is entered into a cell
   Displayed value – what is displayed in the cell
           Formula – an instruction to the program to calculate a
            number
           Function – a preprogrammed formula




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Cell Contents: Formula

           Calculation instruction
           Contains
               Cell address
               One or more arithmetic operators
               Functions
           Result appears in the cell containing the formula
           Calculation appears in the formula bar




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Ranges

      A group of one or more
       adjacent cells occurring
       in a rectangular shape
           The program treats the
            range as a unit
           A range is referred to by
            its upper-left and lower-
            right cells, for example
            E7:G14




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Spreadsheet Features

   Security
           Cells can be protected so the user doesn’t
            accidentally destroy complex formulas
           Password protection can prevent anyone from
            making changes to the worksheet
   Decoration
           Add borders or colors to cells or ranges
           Change the color of fonts
           Add clip art


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Planning the Spreadsheet

   Create a sketch of the
    spreadsheet
           Show how labels and data
            should appear
           Specify any formulas
            and/or functions needed




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Business Graphics

   Graphics that represent data in a
    visual, easily understood format
           Generate and sustain interest
           Graphs easily reveal trends that
            could be lost if buried in long
            columns of numbers
   Two types:
           Analytical graphics
           Presentation graphics




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Line Graphs

   Illustrate multiple
    comparisons
   Data is plotted in plot
    area, then connected
    by a line




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Computers:
Tools for an Information Age



Chapter 13
Database Management Systems:
Getting Data Together
The Hierarchy of Data

   Field – a group of one or more characters that has a
    specific meaning
           The smallest meaningful unit of data
           Describes one characteristic of a person, place, or thing
   Record – the set of fields containing data about a person,
    place, or thing
   File – a collection of related records




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Primary Key

   A field that uniquely identifies a record
           SalesID can be a primary key for the Salesperson
            table
           Once a SalesID appears in the table, no other
            salesperson can have that ID




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Relational Model

   Data organized in table
    format
           Columns represent fields
           Rows represent records
   Tables related by
    primary/foreign key
    relationship
   Most current database
    development uses this
    model


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Integrity Constraints

   Define acceptable values for a field
           For example, the value of a month cannot be
            greater than 12
   Primary keys cannot be duplicated
   Foreign keys cannot be used unless they
    exist as a primary key
           A SalesID that is used in the customer table must
            exist as a primary key in the salesperson table



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Creating the Database

   Consider your needs
           Reports you will need
           Inquiries you will want to make




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Setting Up the File Structure

   Design the structure for
    each table
           Define the table
           Define each field in the table
           Define primary key
   Set up the table in design
    view




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Entering the Data

   Enter data into the tables in
    datasheet view
   Enter data into the tables by
    using a graphical form




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Data Retrieval

   Involves extracting the desired data
   Two primary forms of data retrieval
           Queries
           Reports




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Queries

   You present a set of criteria; the DBMS
    selects matching data from the database
   Use a query language
           Structured Query Language (SQL) is supported
            by most relational databases
           Query-by-example (QBE) uses a graphical
            interface to generate the SQL
           Display results in a table-like grid



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Data Warehouses

   Contain data that has been captured in
    company databases
           Can contain data that has been gathered from
            external sources
   Use a variety of analytical tools




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Analytical Tools

   Online analytical processing (OLAP) software
           Analyzes data from all databases in the data
            warehouse
           Provides different “views” of the same data
   Data mining uses sophisticated statistical and
    artificial intelligence techniques
           Looks for previously unrecognized patterns,
            relationships, and trends among the data




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Computers:
Tools for an Information Age



Chapter 14
Systems Analysis and Design:
The Big Picture
The Systems Development Life Cycle
(SDLC)
Phases for Developing a System:
 Preliminary investigation

 Analysis

 Design

 Development

 Implementation




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Preliminary Investigation: Defining the
Problem
   Two points that must be
    agreed upon
           The nature of the problem
           The scope (boundaries) of the
            problem
   Agreeing on the problem
    helps define the objectives of
    the system




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Systems Analysis

   Studying an existing system to determine how it
    works and how it meets users’ needs
           Typically happens as a result of some impetus for change,
            combined with the authority to make the change




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Individuals Involved in Systems Analysis

   Systems analyst – performs analysis and
    design
           Not programming (but may on occasion)
   Client – the person or organization
    contracting to have the work done
   User – the people who will have contact with
    the system



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Data Gathering

   A number of techniques can be used
           Written documents
           Interviews with users and managers
                Structured interview – includes only questions that
                 have been written out in advance
                Unstructured interview – interviewer has a general
                 goal but few, if any questions prepared
           Questionnaires
           Observation
           Sampling


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System Requirements

   A detailed list of things the
    system must be able to do
           The design of the new system
            will be based on these
            requirements
           Analyst and management must
            come to a clear agreement on
            requirements




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Key Decisions
   Write custom software or buy a software
    package (make or buy decision)
           Software packages will often need to be
            customized
   Outsource software development or create
    in-house
           In-house design requires client to have technical
            expertise
   Develop alternatives (candidates)
           All candidates meet the client’s requirements but
            with variations in features and cost

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Systems Design

   The process of developing a plan for an improved
    system, based on the result of the systems analysis




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Systems Design

   Develop detailed design specifications that
    will satisfy requirements
           Output requirements
           Input requirements
           Files and databases
           System processing
           System controls and backups




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Prototyping

   Building a model of the system
           Typically a limited working system or subset of a system
           Developed very quickly
           Designed to give the user an idea of what the system will
            look like
   Computer-aided software engineering (CASE) tools
           Automate many of the tasks of the development process




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System Development

   Schedule and monitor the two principal activities
           Programming
           Testing
   There are several project scheduling tools
    available




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Testing

   Unit testing – verifies that individual program
    units work
           Perform testing with test data
   System testing – determines whether all
    program units work together as planned
   Volume testing – uses real data in large
    amounts
           Determines whether the system can handle a
            large volume of data


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Implementation

   Steps involved in starting the new system
           Training
           Equipment conversion
           File conversion
           System conversion
           Auditing
           Evaluation
           Maintenance


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System Conversion

   Four approaches
           Direct conversion – the user simply stops using the old
            system and starts using the new one
           Phased conversion – the system is implemented one part
            at a time
           Pilot conversion – the entire system is used by a
            designated set of users
           Parallel conversion – the old and new systems are both
            used until users are satisfied the new system works




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Training

   Teach users how to use the system
           The system will do no better than the people
            using it
           Develop user’s manual to aid users who are not
            familiar with the system
           Hands-on training is best




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