Computer Software Ch'2A,B,C Ch'15D,E

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Computer SoftwareCh.2-A,B,C Ch.15-D,E

• FALL 2000
• Rob Wolfe

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Goal

• Determine legal restrictions on SW
• Describe the purpose of OS
• Recognize DOS, Windows, UNIX, Mac OS
• Categorize SW as either system or application
• Determine best SW for specific tasks
• Recognize the 4 generations of Programming
  Languages

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Computer Programs

• A computer program is a set of instructions that
  tells a computer how to carry out a task.
• Computer programs are written in a programming
  language that computers can understand.

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Computer Programs

• A sample program

program Conversion (input,output) const
inchesPerFoot 12 centimetersPerInch
2.54 var feet, inches, lengthInInches
integer centimeters real begin
write(What is the length in feet and inches?)
readln(feet,inches) lengthInInches
inchesPerFoot feet inches centimeters
centimetersPerInch lengthInInches
writeln(The length in centimeters is,
centimeters12) end
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Computer Software

• Software (as opposed to hardware) is a set of
  statements or instructions to be used directly or
  indirectly in a computer in order to bring about
  a certain result.
• Same as program? Data?
• Shareware
• Public domain

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Software License

• Single-user license limits use of software to
  one user at a time
• Multiple-user license allows more than one user
  to use particular software
• Concurrent-user license allows a certain number
  of software copies to be used at same time
• Site license allows software to be used on all
  computers at specific location

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Classifying Software

• System Software
• Operating Systems
• Device Drivers
• Utilities
• Application Software
• Majority
• Programming Languages
• Four generations of programming languages
• VB Lab

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Software Relationships
Programming Languages
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Operating Systems

• Roles of OS
• I/O control
• System resource allocation
• Hardware failure detection
• Security maintenance
• OS examples
• UNIX
• DOS
• Windows
• OS/2
• MAC OS

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Application Software

• What is
• productivity software?
• A suite?
• groupware?
• Before you graduate, make sure you become very
  handy with
• one word-processor
• one spreadsheet software package
• one database management system
• one presentation software package

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Application Software

• Task-specific software, e.g.
• Document production
• Graphics - bitmap, vector, 3-D rendering,
  animation
• Presentation
• Numeric analysis
• Data management
• Connectivity
• Accounting Finance
• Various business software - Horizontal v. Vertical

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Programming Languages

• Procedural v. Declarative
• Low-level v. High-level Languages
• Compilation v. Interpretation

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Programming Languages

• Four Generations
• 1st generation 1940s, Machine Language
• 2nd generation 1950s, Assembly Language
• 3rd generation 1960s, Proliferation
• 4th generation 1970s, SQL

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First Generation

• 1940s
• Machine Language
• Characteristics
• Binary code
• Extremely cryptic
• Tight coupling between machine and program
• Not portable

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Second Generation

• 1950s
• Assembly Language
• Characteristics
• A little less cryptic
• Still strong coupling between HW and SW
• Thus, not portable
• Up to this language is considered Low-level

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Third Generation

• 1960s
• Proliferation of Languages
• BASIC, COBOL, Pascal, FORTRAN, C
• Characteristics
• High-level
• Compiling v. Interpreting
• Still dominant
• Up to this generation is procedural

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Fourth Generation

• 1970s
• SQL (Structured Query Language)
• Characteristics
• Non-procedural, or Declarative
• Syntax is closer to natural language
• More powerful

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VB Programming

• Structured Programming
• Hierarchy Chart
• Sequence, Selection, Iteration
• VB I.20 (Problem 3)

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In review

• Determine legal restrictions on SW
• Describe the purpose of OS
• Recognize DOS, Windows, UNIX, Mac OS
• Categorize SW as either system or application
• Determine best SW for specific tasks
• Recognize the 4 generations of Programming
  Languages