Chapter 2 Computer Software

1
Chapter 2Computer Software

• MIS 311
• Jakob Iversen

2
Software History and Significance

• 1950s Hardware was expensive. Software was less
  important and less expensive.
• Today software comprises a much larger
  percentage of the cost of modern computer systems
• The Software Crisis Many software projects are
  delivered late, over budget with inferior
  quality, and does not meet requirements/expectatio
  ns
• software applications cant keep up with rapidly
  changing business conditions and rapidly evolving
  technologies
• new applications must be developed quickly, and
  existing software must also be maintained (est.
  80 effort on maintenance)
• more complexity, leads to more bugs
• testing and debugging software is expensive and
  takes time

3
Software Model A Layered View
4
Software Classifications
5
System Software

• Programs that control and support the computer
  system
• Supports application software by directing the
  basic functions of the computer
• Facilitates programming, testing, and debugging
  of computer programs
• Usually independent of any specific type of
  application

6
Operating Systems Functionality

• Common Hardware Functions
• User Interface
• Hardware Independence
• Memory Management
• File Management

• Processing Tasks
• Multitasking and time-sharing
• Networking Capability
• Access to System Resources
• Security

7
Major Desktop OS
MS-DOS
Windows 3.xx
Windows 98
Windows 95
Windows NT
Windows 2000
Windows XP
IBMs OS/2
Macintosh Operating System
Linux
UNIX
Java Operating System (JavaOS)
8
(No Transcript)
9
Windows 3.11
10
Windows 95
11
Windows XP
12
Linux (KDE 3)
13
Other Systems Control Program

• (Helps you use the computer)
• Backup software
• Antivirus software
• Uninstaller software
• File handling
• Drivers (for various peripherals)
• Performance monitors
• Security monitors

14
Application Software
Direct a computer system to perform specific
information processing activities and provide
functionality for users (lets you do real work)
15
(No Transcript)
16
Personal Application Software

• An off-the-shelf application program not linked
  to any specific business function, but instead
  supports general types of processing

Data management
Spreadsheet
Word processing
Desktop publishing
Publishing
Communications
Graphics
Multimedia
Speech recognition software
GroupWare
17
Software Suites

• Collections of application software packages that
  integrate the functions of the packages
• Examples Microsoft Office, Star Office, Corel
  Word Perfect Office, and Lotus SmartSuite
• Generally include spreadsheet, word processor,
  database, and graphics package
• Ability to move data and diagrams among
  individual application

18
Enterprise Application Software
19
Supply Chain Management
20
Enterprise Resource Planning Vendors

• 25.1 SAP
• 7.0 Oracle (trying to buy PeopleSoft)
• 6.5 PeopleSoft
• ?? JD Edwards (bought by PeopleSoft)
• 5.4 Sage
• 4.9 Microsoft
• 51.1 Other
• Total revenue in 2002 5 billion, down from 5.5
  billion
• Source Gartner Dataquest (June 2003)
  http//www4.gartner.com/5_about/press_releases/pr1
  8june2003a.jsp

21
Problems with ERP

• Very complex systems
• Require changes to all/most parts of the
  organization
• Very long implementation process
• 12-24 months
• Systems require customization
• Customizations may make it difficult to upgrade
• Difficult to move to different vendor
• Customization experts in short supply
• More info http//www.du.edu/atanner/whatiserp.ht
  m

22
Programming Languages

• Different languages for different purposes
• Tradeoff between easy to program
  (programmer-friendly) vs. Efficiency in execution
  (computer-friendly)

23
Example Assembly Language (2GL)

• SUB AX, CX
• LP ADD AX, BX
• ADD BX, 2
• CMP DX, BX
• JNS LP

• Mnemonics
• Need to know how the CPU works
• Typically no OS
• Still in use where speed is very important
  often embedded systems

24
Procedural Language (Pascal), 3GL

• Program MyAddition
• Var
• a, b, c int
• Begin
• Writeln (This is fun)
• a2 b5
• While altb do begin
• a a 1
• end
• c a b
• Writeln (a,,b,,c)
• End.

• Sequence
• Conditions
• Loops
• Procedures/functions
• Other 3GL Languages
• C, COBOL, Fortran, ...

25
4GL Non-procedural (SQL)

• Stating an outcome
• SELECT (Customer_Name and Customer_Address)
• FROM Customer_Table
• WHERE Credit_Limit gt 5000
• Other languages state facts and rules
• Fact 1 Jane is Alans Mother
• Fact 2 Mary is Janes sister
• Rule 1 An aunt is the sister of ones mother or
  the sister of ones father
• Inference engine Is Mary Alans aunt?
• Languages
• PL/1, Lisp, SQL

26
Programming Languages (continued )

• Visual Programming Languages
• used within a graphical environment
• example Visual Basic and Visual C
• popular with non technical users
• Hypertext Markup Language (HTML)
• standard language used in World Wide Web
• Plain text file describes page layout, references
  other files to be displayed (images, audio,
  video, and executable computer programs)
• Example!

27
Programming Languages (continued )

• Object-Oriented Programming Languages (OOP)
• Objects model real-world phenomena by combining
  data and instructions
• Java, C, Eiffel, Smalltalk

28
Object Oriented Programs

• Inheritance
• Instantiation
• Class -gt Object
• Communication

29
Message Passing in Objects
30
Reusable Code in Object-Oriented Programming
31
How an Interpreter Works
32
How a Compiler Works
33
Coming up...

• Need more detail?
• Go to www.howstuffworks.com and check out the
  Computer section.
• Thursday
• Due Lab 3
• Tuesday
• Networks (Internet, Intranet, Extranet, )
• Stair, Chapter 4