1. Chapter 2 Computer Software
MIS 311
Jakob Iversen

2. Software History and Significance
1950’s: 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/expectations
software applications can’t 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 XP
IBM’s OS/2
Macintosh Operating System
Linux
UNIX
Java Operating System (JavaOS)

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. Direct a computer system to perform specific information processing activities and provide functionality for users (lets you do real work)
Application Software

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
Desktop publishing
Publishing
Word processing
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)

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:

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’);
a:=2; b:=5;
While a<b 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 > 5000
Other languages state facts and rules
Fact 1: Jane is Alan’s Mother
Fact 2: Mary is Jane’s sister
Rule 1: An aunt is the sister of one’s mother or the sister of one’s father
Inference engine: Is Mary Alan’s 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 -> 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? Thursday Tuesday
Go to and check out the Computer section.
Thursday
Due: Lab 3
Tuesday
Networks (Internet, Intranet, Extranet, …)
Stair, Chapter 4