1 Chapter 2 Computer Software MIS 311 Jakob Iversen.
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Transcript of 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
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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
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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
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Major Desktop OS
MS-DOS Windows 3.xx
Windows 95Windows 98
Windows NT Windows 2000
IBM’s OS/2
Macintosh Operating SystemUNIX
Java Operating System (JavaOS)
Linux
Windows XP
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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
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Application Software
Direct a computer system to perform specific information processing activities and provide functionality for users (lets you do real work)
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Personal Application Software
An off-the-shelf application program not linked to any specific business function, but instead supports general types of processing
SpreadsheetData management
Word processingDesktop publishing Publishing
Graphics Multimedia Communications
Speech recognition software GroupWare
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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
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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/pr18june2003a.jsp
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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.htm
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Programming Languages
Different languages for different purposes Tradeoff between easy to program (programmer-
friendly) vs. Efficiency in execution (computer-friendly)
… ..……
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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
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Procedural Language (Pascal), 3GLProgram MyAddition;
Vara, b, c: int;
BeginWriteln (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, ...
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4GL: Non-procedural (SQL)
Stating an outcome:SELECT (Customer_Name and Customer_Address)FROM Customer_TableWHERE Credit_Limit > 5000
Other languages state facts and rulesFact 1: Jane is Alan’s MotherFact 2: Mary is Jane’s sisterRule 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
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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!
Programming Languages (continued …)
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Programming Languages (continued …)
Object-Oriented Programming Languages (OOP)• Objects model real-world phenomena by
combining data and instructions
• Java, C++, Eiffel, Smalltalk