4 1 Computer Software Ch.2-A,B,C; Ch.15-D,E FALL 2000 Rob Wolfe

4 DIT Wolfe 2Goal Determine legal restrictions on SW Determine legal restrictions on SW Describe the purpose of OS Describe the purpose of OS Recognize DOS, Windows, UNIX, Mac OS Recognize DOS, Windows, UNIX, Mac OS Categorize SW as either system or application Categorize SW as either system or application Determine best SW for specific tasks Determine best SW for specific tasks Recognize the 4 generations of Programming Languages Recognize the 4 generations of Programming Languages

4 DIT Wolfe 3 Computer Programs A computer program is a set of instructions that tells a computer how to carry out a task. 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. Computer programs are written in a programming language that computers can understand.

4 DIT Wolfe 4 Computer Programs A sample program 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’, centimeters:1:2) end 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’, centimeters:1:2) end

4 DIT Wolfe 5 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. 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? Same as program? Data? Shareware Shareware Public domain Public domain

4 DIT Wolfe 6 Software License Single-user license — limits use of software to one user at a time 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 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 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 Site license — allows software to be used on all computers at specific location

4 DIT Wolfe 7 Classifying Software System Software System Software Operating Systems Device Drivers Utilities Application Software Application Software Majority Programming Languages Programming Languages Four generations of programming languages VB Lab

4 DIT Wolfe 8 Software Relationships Programming Languages

4 DIT Wolfe 9 Operating Systems Roles of OS Roles of OS I/O control System resource allocation Hardware failure detection Security maintenance OS examples OS examples UNIX DOS Windows OS/2 MAC OS

4 DIT Wolfe 10 Application Software What is … What is … productivity software? A suite? groupware? Before you graduate, make sure you become very handy with … 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

4 DIT Wolfe 11 Application Software Task-specific software, e.g.: 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

4 DIT Wolfe 12 Programming Languages Procedural v. Declarative Procedural v. Declarative Low-level v. High-level Languages Low-level v. High-level Languages Compilation v. Interpretation Compilation v. Interpretation

4 DIT Wolfe 13 Programming Languages Four Generations Four Generations 1st generation 1940s, Machine Language 2nd generation1950s, Assembly Language 3rd generation1960s, Proliferation 4th generation1970s, SQL

4 DIT Wolfe 14 First Generation 1940s 1940s Machine Language Machine Language Characteristics Characteristics Binary code Extremely cryptic Tight coupling between machine and program Not portable

4 DIT Wolfe 15 Second Generation 1950s 1950s Assembly Language Assembly Language Characteristics Characteristics A little less cryptic Still strong coupling between HW and SW Thus, not portable Up to this language is considered Low-level

4 DIT Wolfe 16 Third Generation 1960s 1960s Proliferation of Languages Proliferation of Languages BASIC, COBOL, Pascal, FORTRAN, C Characteristics Characteristics High-level Compiling v. Interpreting Still dominant Up to this generation is procedural

4 DIT Wolfe 17 Fourth Generation 1970s 1970s SQL (Structured Query Language) SQL (Structured Query Language) Characteristics Characteristics Non-procedural, or Declarative Syntax is closer to natural language More powerful

4 DIT Wolfe 18 VB Programming Structured Programming Structured Programming Hierarchy Chart Hierarchy Chart Sequence, Selection, Iteration Sequence, Selection, Iteration VB I.20 (Problem #3) VB I.20 (Problem #3)

4 DIT Wolfe 19 In review Determine legal restrictions on SW Determine legal restrictions on SW Describe the purpose of OS Describe the purpose of OS Recognize DOS, Windows, UNIX, Mac OS Recognize DOS, Windows, UNIX, Mac OS Categorize SW as either system or application Categorize SW as either system or application Determine best SW for specific tasks Determine best SW for specific tasks Recognize the 4 generations of Programming Languages Recognize the 4 generations of Programming Languages