Computers:Tools for an Information Age

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

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Secondary Storage

Separate from the computer itselfSoftware 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 pagesOptical disk can hold equivalent of 500 books

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Benefit: Reliability

Data in secondary storage is relatively safeSecondary storage is highly reliableMore 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 cabinetsReliable and safe data is less expensive to maintainGreater 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 surfaceHard 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 unitAll 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 capacityLaser scans disk and picks up light reflections from disk surfaceCategorized by read/write capability

Read-only media - user can read from, but not write to diskWrite-once, read-many (WORM) - user can write to disk onceMagneto-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 diskPrimary medium for software distribution

CD-R - drive can write to disk onceDisk 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-ROMsCapacity up to 17GBAllows for full-length moviesSound 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 stripingIncreases performance

Raid level 1 duplicates data on several drives

Called disk mirroringIncreases fault tolerance

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Organizing and Accessing Stored Data

CharacterFieldRecordFileDatabase

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Field

A set of related charactersDescribes 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 fieldsFor the university, all of the fields for one student constitute one record

Computers:Tools for an Information Age

Chapter 10Security and Privacy:Computers and the Internet

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Security and Privacy

Security – data stored on computer must be kept safePrivacy – private data must be kept from prying eyes

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Methods Computer Criminals Use

BombData diddlingDenial of service attacksPiggybackingSalami technique

ScavengingTrapdoorTrojan horseZapping

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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 siteHackers 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 virusCan cause tremendous damage to computer and data filesCan be preventedCommon computer myths

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Spamming

Mass advertising via e-mailCan overflow your e-mail inboxBogs 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 driveFile is sent back to the server each time you visit that site

Stores preferences, allowing Web site to be customizedStores passwords, allowing you to visit multiple pages within the site without logging in to each oneTracks surfing habits, targeting you for specific types of advertisements

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Preventing Spam

Many ways you can minimize junk e-mailBe careful how you give out your e-mail addressFiltering software allows you to block messages or send them to designated foldersDon’t register at Web sites without a promise the Web site will not sell your informationNEVER 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 firewallProtects the organization from unauthorized accessCan 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 themOnce 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 destructionSeveral approaches

Manual servicesBuying time at a service bureauConsortium

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

Computers:Tools for an Information Age

Chapter 12Spreadsheets and Business Graphics:Facts and Figures

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Electronic Spreadsheets

A computerized version of a paper spreadsheet Benefits

Eliminates much of the tediumCalculations are error-freeWorksheet is automatically recalculated when you change one value or calculationPerforms “what-if” analysis

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Cells and Cell Addresses

Spreadsheet is divided into rows and columnsA cell is the intersection of a row and a column

Cell is known by its addressAddress 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 spreadsheetValue – an actual number that is entered into a cellDisplayed value – what is displayed in the cell

Formula – an instruction to the program to calculate a numberFunction – a preprogrammed formula

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Cell Contents: Formula

Calculation instructionContains

Cell addressOne or more arithmetic operatorsFunctions

Result appears in the cell containing the formulaCalculation 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 unitA range is referred to by its upper-left and lower-right cells, for example E7:G14

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Spreadsheet Features

SecurityCells can be protected so the user doesn’t accidentally destroy complex formulasPassword protection can prevent anyone from making changes to the worksheet

DecorationAdd borders or colors to cells or rangesChange the color of fontsAdd clip art

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Planning the Spreadsheet

Create a sketch of the spreadsheet

Show how labels and data should appearSpecify 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 interestGraphs easily reveal trends that could be lost if buried in long columns of numbers

Two types:Analytical graphicsPresentation graphics

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Line Graphs

Illustrate multiple comparisonsData is plotted in plot area, then connected by a line

Computers:Tools for an Information Age

Chapter 13Database Management Systems:Getting Data Together

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The Hierarchy of Data

Field – a group of one or more characters that has a specific meaning

The smallest meaningful unit of dataDescribes one characteristic of a person, place, or thing

Record – the set of fields containing data about a person, place, or thingFile – a collection of related records

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Primary Key

A field that uniquely identifies a recordSalesID can be a primary key for the Salesperson tableOnce 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 fieldsRows represent records

Tables related by primary/foreign key relationshipMost current database development uses this model

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Integrity Constraints

Define acceptable values for a fieldFor example, the value of a month cannot be greater than 12

Primary keys cannot be duplicatedForeign 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 needsReports you will needInquiries you will want to make

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Setting Up the File Structure

Design the structure for each table

Define the tableDefine each field in the tableDefine primary key

Set up the table in design view

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Entering the Data

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

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Data Retrieval

Involves extracting the desired dataTwo primary forms of data retrieval

QueriesReports

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Queries

You present a set of criteria; the DBMS selects matching data from the databaseUse a query language

Structured Query Language (SQL) is supported by most relational databasesQuery-by-example (QBE) uses a graphical interface to generate the SQLDisplay 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 warehouseProvides 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

Computers:Tools for an Information Age

Chapter 14Systems Analysis and Design:The Big Picture

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The Systems Development Life Cycle (SDLC)Phases for Developing a System:

Preliminary investigationAnalysisDesignDevelopmentImplementation

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Preliminary Investigation: Defining the Problem

Two points that must be agreed upon

The nature of the problemThe 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 doneUser – the people who will have contact with the system

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Data Gathering

A number of techniques can be usedWritten documentsInterviews with users and managers

Structured interview – includes only questions that have been written out in advanceUnstructured interview – interviewer has a general goal but few, if any questions prepared

QuestionnairesObservationSampling

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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 requirementsAnalyst and management must come to a clear agreement on requirements

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Key DecisionsWrite 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 requirementsInput requirementsFiles and databasesSystem processingSystem controls and backups

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Prototyping

Building a model of the systemTypically a limited working system or subset of a systemDeveloped very quicklyDesigned to give the user an idea of what the system will look like

Computer-aided software engineering (CASE) toolsAutomate many of the tasks of the development process

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System Development

Schedule and monitor the two principal activitiesProgramming 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 dataSystem testing – determines whether all program units work together as plannedVolume 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 systemTrainingEquipment conversionFile conversionSystem conversionAuditingEvaluationMaintenance

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System Conversion

Four approachesDirect conversion – the user simply stops using the old system and starts using the new onePhased conversion – the system is implemented one part at a timePilot conversion – the entire system is used by a designated set of usersParallel 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 systemThe system will do no better than the people using itDevelop user’s manual to aid users who are not familiar with the systemHands-on training is best