Computer Software

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CHAPTER 3

• Computer Software

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THE STORED PROGRAM CONCEPT

• COMPUTER IS A BINARY SYSTEM
• PROGRAM A set of instructions telling the
  computer what to do
• INSTRUCTION Individual step or operation in a
  program
• MACHINE LANGUAGE Translated instruction
  understood by particular model of computer

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KEY TYPES OF SOFTWARE

• APPLICATION SOFTWARE Programs written to
  accomplish particular tasks for computer users
• SUPPORT SOFTWARE or SYSTEM SOFTWARE Programs
  that support application software in producing
  needed output. Does not directly produce output
  needed by users

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Spheres of Influence Application Software

• Two or more people who work together to achieve
  a
• common goal
• Systems that support information sharing, group
• scheduling, group decision making, and
  conferencing

Workgroup
Personal
Enterprise

• programs that support
• the firm in its
• interaction with its
• environment
• order entry, billing

• programs that serve the
• needs of an individual user
• word processing,
• spreadsheets, databases,
• e-mail

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Application SoftwareGeneral-Purpose vs.
Application-Specific

• General-purpose application programs programs
  that perform common information processing jobs
  for end users
• Examples include
• Word processing
• Spreadsheet
• Database management
• Graphics
• Web browsers
• Electronic mail
• Groupware

• Application-specific programs that direct the
  processing required for a particular use
• Examples include
• Business Applications - accounting, sales
  management, eCommerce
• Science and Engineering Applications research
  and development
• Personal Applications
• Education and Entertainment Applications

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Web Browsers
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Application Suites

• Software suites are a combination of the most
  widely used productivity packages that come
  bundled together
• Suites integrate software packages for web
  browsing, word processing, spreadsheets,
  presentation graphics, database management,
  personal information management, and more
• Examples Microsoft Office, Lotus SmartSuite, and
  Corel WordPerfect Office

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Groupwarehelps teams work together to accomplish
group assignments

• Groupware products (Lotus Notes, Novell
  GroupWise, Microsoft Exchange, Netscape
  Communicator) support collaboration through
• Electronic Mail
• Discussion groups and databases
• Scheduling
• Task management
• Data, audio, and videoconferencing
• Internet, corporate intranets and extranets to
  make collaboration possible on a global scale by
  virtual teams located anywhere in the world.
• Joint web page development
• Publish project news and progress reports
• Working jointly on documents stored on web servers

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EVOLUTION OF PROGRAMMING LANGUAGE

• 1st Generation Machine language - binary
  language designed for particular computer
• 2nd Generation Assembly language - substituted
  mnemonic operation codes and addresses,
  translated to machine language by assembler
• 3rd Generation Procedural language - FORTRAN,
  COBOL, C - translated to machine language by
  compiler or interpreter. Example COBOL
• 4th Generation Nonprocedural language. Tell what
  to do, not how to do it, order not important.
  Translate to machine language by compiler or
  interpreter. Example FOCUS

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OTHER LANGUAGES

• NATURAL LANGUAGES User types in or speaks
  English, computer evolves program
• HYPERTEXT MARKUP LANGUAGE (HTML) Code used to
  develop World Wide Web (WWW) pages and sites
• eXtensible Markup Language (XML) Used for data
  exchange on WWW

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HTML, XML and Java

• HTML and Java have become vital tools for
  building multimedia web pages, web sites, and
  web-based applications
• HTML is a page description language that creates
  hypertext or hypermedia documents
• XML describes the contents of web pages by
  applying identifying tags or contextual labels to
  the data in web documents
• Java
• is an object-oriented programming language
• is computing platform independent
• Is designed for realtime, interactive, web-based
  network applications
• Java applications consist of small application
  programs called applets, which can be executed by
  any computer and any operating system anywhere in
  a network

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OBJECT-ORIENTED PROGRAMMING (OOP)

• COMPUTER PROGRAMMING BASED ON CREATING, USING SET
  OF OBJECTS Object combines data and methods (or
  chunks of programs)
• EXAMPLES C, Smalltalk, Java

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Categories of Programming Languages
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Programming Language Translation
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Programming Languages Terminology

• Language translator
• Systems software that converts a programmers
  source code into its equivalent in machine
  language.
• Source code
• High-level program code written by the
  programmer.
• Object code
• Another name for machine language code.

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SUPPORT (SYSTEMS) SOFTWARE

• OPERATING SYSTEMS Helps maximize work done,
  eases workload of users
• JOB CONTROL LANGUAGE Allows users to communicate
  with operating systems
• MULTIPROGRAMMING Large computers can run
  multiple programs simultaneously. Time-driven
  approach is time-sharing
• MULTITASKING Allows small computers to work on
  several programs interactively
• VIRTUAL MEMORY Allows computer to run portions
  of a large program as required, saving use of
  main memory
• MULTIPROCESSING Multiple CPUs divide workload,
  increases efficiency

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Functions of an Operating System
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OPERATING SYSTEMSa set of programs that control
the hardware and acts as an interface with
application programs
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User Interface

• User Interface
• A function of the operating system that allows
  individuals to access and command the computer.
• Command-Based User Interface
• A particular user interface that requires text
  commands be given to the computer to perform
  basic activities.
• Graphical User Interface (GUI)
• A user interface that uses pictures (icons) and
  menus displayed on the screen to send commands to
  the computer system.

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GRAPHICAL USER INTERFACE (GUI)

• MOUSE A standard pointing device
• ICON Graphic or label on screen associated with
  task or operation
• 32-BIT OPERATING SYSTEM Operating system handles
  32 bits at a time
• CLICKING MOUSE ON ICON INITIATES TASK

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Software Concepts

• Virtual Memory
• Memory that allocates space in secondary storage
  to supplement the immediate, functional memory
  capacity of RAM.
• Paging
• A function of virtual memory that allows the
  computer to store currently needed pages in RAM
  while the rest of these programs wait in
  secondary storage.

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Utility Programs

• merge and sort sets of data,
• keep track of computer jobs being run,
• compress files of data before they are stored or
  transmitted over a network, and
• perform other important tasks.

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SOURCES OF OPERATING SYSTEMS

• PROPRIETARY Written for particular computer
  class or system. Examples Windows 98, Windows
  2000
• OPEN SYSTEM Not tied to specific platform.
  Examples UNIX, Linux
• NETWORK OPERATING SYSTEM (NOS) Manages network
  resources, local area networks

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DATABASE MANAGEMENT SYSTEM (DBMS)

• SUPPORT SOFTWARE USED TO CREATE, MANAGE, AND
  PROTECT ORGANIZATIONAL DATA
• DBMS Software that manages a database, works
  with operating system to store and modify data
  and to make data accessible in authorized ways

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TYPES OF DBMSs

• HIERARCHICAL Data arranged in a top-down,
  organization chart fashion
• NETWORK Data arranged like cities on a highway
  systems, often with multiple paths between pieces
  of data
• RELATIONAL Data arranged into simple tables, and
  records are related by storing common data in
  each of the associated tables

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FILING METHODS

• INDEXED SEQUENTIAL ACCESS METHOD (ISAM)
• EACH RECORD IDENTIFIED BY KEY
• GROUPED IN BLOCKS AND CYLINDERS
• KEYS IN INDEX
• VIRTUAL STORAGE ACCESS METHOD (VSAM)
• MEMORY DIVIDED INTO AREAS INTERVALS
• DYNAMIC FILE SPACE
• VSAM WIDELY USED FOR RELATIONAL DATABASES
• DIRECT FILE ACCESS METHOD

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COMPONENTS OF DBMS

• DATA DEFINITION LANGUAGE Defines data elements
  in database
• DATA MANIPULATION LANGUAGE Manipulates data for
  applications
• DATA DICTIONARY/DIRECTORY Formal definitions of
  all variables in database, controls variety of
  database contents

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Database (Access / Approach / Paradox) Stores,
manipulates, and retrieves data
(Figure 4.10)
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STRUCTURED QUERY LANGUAGE (SQL)

• EMERGING STANDARD
• DATA MANIPULATION LANGUAGE
• FOR RELATIONAL DATABASES

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ADVANTAGES OF RELATIONAL DBMS

• NEW DATA ELEMENTS CAN EASILY BE ADDED AS NEW
  NEEDS ARISE
• NEW RELATIONSHIPS CAN BE CREATED AS NEW
  QUERY/REPORTING NEEDS CHANGE
• FEWER DATA CONSISTENCY PROBLEMS DUE TO LESS
  REDUNDANT DATA STORAGE
• MORE USER FRIENDLY TOOLS

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COMPUTER-AIDED SOFTWARE ENGINEERING (CASE)

• HELPS AUTOMATE SOFTWARE DEVELOPMENT Used by
  computer professionals to help automate software
  development
• MAY INCLUDE
• upper-CASE (requirements definition and design)
• lower-CASE (code generation)
• I-CASE or integrated-CASE

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CHANGING NATURE OF SOFTWARE

• MORE HARDWIRING OF SOFTWARE AND MORE MICROCODE
• MORE COMPLEXITY OF HARDWARE/SOFTWARE ARRANGEMENTS
• LESS CONCERN WITH MACHINE EFFICIENCY
• MORE PURCHASED APPLICATIONS AND MORE PORTABILITY
  OF THESE APPLICATIONS FROM ONE COMPUTER PLATFORM
  TO ANOTHER

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CHANGING NATURE OF SOFTWARE

• MORE PROGRAMMING USING OBJECT-ORIENTED AND VISUAL
  LANGUAGES, IN LARGE PART BECAUSE OF EMPHASIS ON
  GUIs
• MORE EMPHASIS ON APPLICATIONS THAT RUN ON
  INTRANETS AND THE INTERNET
• MORE USER DEVELOPMENT
• MORE USE OF PERSONAL PRODUCTIVITY SOFTWARE ON
  MICROCOMPUTERS, ESPECIALLY PACKAGES WITH A GUI

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Trends in Computer Software
Trend Toward Easy-to-Use Multipurpose
Network-Enabled Application Packages for
Productivity and Collaboration
User-written programs Machine languages
Packaged programs Symbolic languages
Operating systems High-level languages
DBMS Fourth-generation languages Microcomputer
packages
Natural object- oriented languages Multipurpos
e graphic-interface network-enabled
expert-assisted packages
Trend Toward Visual or Conversational
Programming Languages and Tools
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CHAPTER 3

• Computer Software