AN INTRODUCTION TO INFORMATION SYSTEMS SOFTWARE IS 340 BY CHANDRA S. AMARAVADI

1. AN INTRODUCTION TO INFORMATION SYSTEMS SOFTWARE IS 340 BY CHANDRA S. AMARAVADI

2. IN THIS PRESENTATION • Intro & types of SW • Overview of systems software • Operating systems • OS functions • Applications Software • Programming languages • Applications of programming languages

3. SOFTWARE Software/SW Program: Detailed instructions to the computer to control information processing operations. COMPUTER OUTPUTS INPUTS INSTRUCTIONS

4. SOFTWARE Operating Systems Sw concerned with the system (Systems sw) Compilers Utility SW Sw for a specific purpose/ (Applications SW or simply “application”) Packaged or “business” or COTs Open source Customized

5. SYSTEMS SOFTWARE

6. SYSTEMS SOFTWARE APPLICATION SOFTWARE OPERATING SYSTEM COMPILERS UTILITY PROGRAM SYSTEM SOFTWARE HARDWARE OPERATING SYSTEM: Software that manages and controls system operations. COMPILERS: Convert a program (the “source program”) to machine code (“object code”). UTILITY: Perform support functions inside the computer e.g. screen savers, file management, network management, data conversion etc.

7. EXAMPLES OF O/S • PC Environment • Windows, Vista • Mac OS • Workstation/server • Unix, Linux

8. OPERATING SYSTEM • COMMON TASKS PERFORMED BY OS • Runs the hardware • CPU, memory etc. • Interacts/monitors users • keyboard commands • passwords etc.

9. APPLICATIONS SOFTWARE

10. APPLICATIONS SOFTWARE Software for a specific purpose CUSTOMIZED APPLICATIONS Inventory Accounting Invoicing ……. BUSINESS SOFTWARE Word processing Spreadsheet Email …….. APPLICATION SOFTWARE SYSTEM SOFTWARE HARDWARE

11. CUSTOMIZED SOFTWARE Software tailored to the needs of a business • “application” generally refers to “customized” • example resume processing, benefits system etc. • developed in 3rd GLs or OO languages • interface may be less finished than business • more expensive

12. BUSINESS SOFTWARE Standardized software for a specific purpose • Example MS Word, Powerpoint etc. • integrated under Windows • Common “look & feel” • Point & Click -- GUI • C&P functionality for DDE • Dynamic, context dependent help Note: DDE stands for Dynamic Data Exchange, C&P for cut and paste

13. OPEN SOURCE SOFTWARE • publicly available or authored by the “public” • aka “public domain” or “shareware” • sometimes subscription/nominal fees • e.g. Zimbra, Winscp downside of open source?

14. PROGRAMMING LANGUAGES

15. PROGRAMMING LANGUAGES • All SW is written in a programming language. • Programming languages have evolved based on factors such as useability, features, and application. • Initially programming languages attempted to control machine components (e.g. memory) • As O/S evolved there was less of a need for programmers to control machine components and more of a need to fulfill user requirements.(e.g reporting)

16. EVOLUTION OF PROGRAMMING LANGUAGES 1st e.g. Machine 2nd e.g. Assembly 3rd e.g. COBOL, C 4th e.g. SQL, macros, Java Script 5th e.g. Prolog, Java, C++ LLL HLL VHLL Note: LLL = Low Level Languages; HLL = High Level Languages VHLL = Very High Level Languages

17. THE FIRST TWO GENERATIONS

18. THE FIRST TWO GENERATIONS • M/C and Assembly languages • low level • hardware dependent • high execution speed

19. ASSEMBLY CODE TO SUBTRACT TWO NUMBERS (FYI) N   ds   1   ; first 8-bit number M   ds   1   ; second 8-bit number P   ds   1   ; third 8-bit number sub8s  ldaa   N   ; first number       suba   M   ; subtract second number ; V bit set if signed overflow       bvc  SetP ; skip if no overflow       bpl   floor ; is positive, should be -128 ceil   ldaa  #127 ; set at maximum (ceiling)       bra   SetPfloor  ldaa  #-128; set to minumum (floor)SetP   staa  P rts

20. HIGH LEVEL vs. LOW LEVEL LANGUAGES The distinction between high level and low level languages is based on the ratio of the # of lines of program code to the # of actions carried out by the system # of program lines : system actions For L.L.L 1:1 For H.L.L 1:10 For VHLL 1:50

21. THE THIRD GENERATION

22. CHARACTERISTICS OF 3rd GLs • languages like COBOL & C • aka “traditional languages”; HLL • 60% of installed apps. • formal - characterized by program structure (not present in 1st, 2nd GLs)

23. CONCEPTUALIZING A PROGRAM (A 3rd GL Program) Data/variables PROGRAM INPUTS OUTPUTS Module1 Module2 Module3 Module4

24. EXAMPLE OF VARIABLES FD BookMasterFile. 01 BMF-Record. 02 BMF-BookNum PIC X(5). 02 BMF-BookTitle PIC X(25). 02 BMF-AuthorName PIC X(25). FD BookSalesFile. 01 BSF-Record. 88 EndOfBSF VALUE HIGH-VALUES. 02 BSF-BookNum PIC X(5). 02 BSF-Copies PIC 99. 02 BSF-SaleStatus PIC X. 88 NormalSale VALUE "N". 01 Book-Rank-TABLE. 02 BookDetails OCCURS 11 TIMES. 03 BookNum PIC 9(5). 03 BookTitle PIC X(25). 03 AuthorName PIC X(25). 03 BookSales PIC 9(4) VALUE ZEROS. 01 Rank PIC 99. 01 PrevBookNum PIC X(5). 01 BookSalesTotal PIC 9(4).

25. EXAMPLE OF A MODULE (COBOL) -- FYI PERFORM Check_BookRank VARYING Rank FROM 10 BY -1 UNTIL Rank < 1. Check_BookRank. IF BookSalesTotal >= BookSales(Rank) MOVE BookDetails(Rank) TO BookDetails(Rank + 1) MOVE BMF-BookNum TO BookNum(Rank) MOVE BMF-BookTitle TO BookTitle(Rank) MOVE BMF-AuthorName TO AuthorName(Rank) MOVE BookSalesTotal TO BookSales(Rank) END-IF.

26. THIRD GENERATION LANGUAGES (3rd GL) • program is modular; has many parts • explicit declaration of variables; • data “Typing” • Acct_bal -- Numeric • Name – AlphaNumeric • use delimiters • procedural

27. THE FOURTH GENERATION

28. FOURTH GENERATION LANGUAGES (4GL) • Associated with various applns. software • Scripting/”macro” language • Examples include SQL, Macro, Java script etc. • Idea is to specify only goals, not how Provide a list of students and their current grade standing. Across Years down Sales, COGs, margin.

29. EXAMPLES OF 4th GLs <SCRIPT LANGUAGE="javascript"> document.write("<FONT COLOR='RED'>This Is Red Text</FONT>") </SCRIPT> Select Product.Name, Product.Price From Product Where Product.price > $4000

30. THE FIFTH GENERATION – AI LANGUAGES

31. FIFTH GENERATION LANGUAGES (5TH GL) • involve symbolic reasoning, pattern matching • as opposed to? • uses “facts”, “predicates” and clauses • purpose of facts & predicates? Sibling(X,Y) :- Parent_of (X,Z), Parent_of(Y,Z).

32. FIFTH GENERATION LANGUAGES (5TH GL) -- FYI.. PREDICATES bank_balance(symbol, symbol) credit_status(symbol, symbol) FACTS bank_balance(Mary, substantial) credit_status(Mary, excellent) bank_balance(Jeff, good) bank_balance(Mark, substantial) credit_status(Mark, good)

33. FIFTH GENERATION LANGUAGES (5TH GL).. FYI CLAUSES approve_loan(X) :- bank_balance(X, substantial), credit_status(X, good). approve_loan(X) :- bank_balance (X, reasonable), credit_status (X, excellent). GOAL approve_loan(Mark)? approve_loan(Mary)? approve_loan(Jeff)?

34. THE FIFTH GENERATION – OO LANGUAGES

35. OBJECT-ORIENTED PROGRAMMING • Appln. a collection of objects, on which actions are taken • Classes are packaged to include data & methods • Methods are actions involving data associated w class • Objects are grouped into classes

36. CONCEPTUALIZING AN OO PROGRAM PROGRAM INPUTS OUTPUTS Class2.method Class1.method Data Data Class4.method Class3.method Data Data

37. CLASSES, OBJECTS.. PROPERTIES, METHODS Employee : John Smith Department: Finance Salary: $60,000 Manager: Steve Update Salary (new_Salary) Change Department(new Department) Change Manager(new Manager)

38. OBJECT ORIENTED CONCEPTS.. WINDOW Win1 Win2 … Win 4 • Which of these are classes and which are objects? • What might be some properties of the class? • What might be methods associated with the class?

39. OBJECT ORIENTED PROGRAMMING Win1 = New Window Win1.height = 10 Win1.breadth = 20 Win1.color = red Win1.open. Win1.resize(15,5). Win1.close.

40. JAVA Machine independent object oriented language introduced by Sun Microsystems (subset of C++) • uses “byte-code” or applets. • applet: tiny program to execute small function • applets sent over network. • interpreted by local interpreter. • run on any computer & operating system.

41. APPLICATIONS OF PROGRAMMING LANGUAGES • L.L.L are efficient from the systems point of view. • All languages need to be converted to m/c. language in order to run on the Hardware. • Parts of O/S in Assembly. • H.L.L and V.H.L.L are convenient from the user’s point of view.

42. APPLICATIONS OF PROGRAMMING LANGUAGES.. • 1st GLs inside m/c • 2nd GLs for parts of system’s sw and some applications sw. • 3rd GL’s for conventional applns. • 4th GLs associated with applications sw. • 5th GL’s used in AI. • OO for conventional applns and Java for web applns.

43. FOR DISCUSSION • What does systems software do? • T/F: O/S is an example of systems software? • What are other examples of systems software? • What is the purpose of a compiler? • What are examples of 5th Generation languages? • What is the fundamental difference between 3rd & OO? • What is Java? Why is it portable?