2. Software Applications

1. 2. Software Applications CS100: The World of Computing John Dougherty Haverford College

2. Outline of Presentation • Hardware vs. Software • Expectations of Software • Algorithm Example • Limits • Future Expectations • Implications

3. Hardware • Tangible – anything you can touch • Devices and components used in computing • Examples • Computer • Disk • Mouse • Printer • Cables

4. Software • Intangible – “can’t touch this” • Examples • Programs • Operating System • Applications • Data • Ideas ? • Emotions ?

5. Other “Wares” • Firmware • In between hardware and software • Typically describes macrocode, hardware burned with instructions used • When computer starts up • Repeatedly used programs for operating system • Shareware • applications available on the honor system

6. Operating System • Software with a Dual Role • User Interface (see AE text Ch. 4) • ..request  accept  execute  feedback  request.. • Text vs. GUI vs. others (voice ?) • Resource Manager • Provides higher-level access to lower-level functions • Operates behind the scenes • Access to devices, memory, etc

7. Operating Systems Examples • Windows (Microsoft) • Most popular • Macintosh (Apple) • First using GUI for PCs • Linux (Linus Torvalds – one guy) • Most recent realization of Unix • Open Source

8. Applications • Programs that accept input data and returns output data Input  Program  Output • Transform the general-purpose computer into a special-purpose tool • Most commercial applications are constructed using large teams • Examples: AE Ch.2 • WP, SS, DB, Presentation, Graphics, Math/Numerical, Browser, Server, Email Client, Games

9. Application Development • a.k.a,. software engineering • Typically a coordinated team effort • Specification • Design • Implementation • Testing • Maintenance

10. Software Errors • Why does software fail if it is intangible? • incorrect or incomplete specification • poor design • bad implementation • Examples • Flight orientation for aircraft • Mars lander

11. Data • Often considered the inert part of software • Used to hold information for computing • Numeric • Alphabetic • Graphic • Audio

12. Data and Hardware • Stored on … • Floppy disk • RAM (Random Access Memory) • CD-ROM • DVD • Tape • Paper ? • “… like music is to an instrument, …”

13. Data Entry • How is data made available to a computer? • By a person • Keyboard and Mouse • Handwriting and Voice • By another computer or other device • Network (wired, wireless) • Sampled (e.g., sound, voltage for pH)

14. Digital vs. Analog • Data must be in digital form • Naturally • Integer numbers • Text characters • Musical notes (A, Bb, B, C, C#, D, Eb, E, F, F#, G, G#) • Converted or Approximated • Analog signals (e.g., voice, weight) • Real numbers (e.g.,p, e, sqrt(2))

15. Expectations of Software • Positive … • Icons represent Applications and Data Files • Menus represent Command Choices • Means to save/recall data, print, send/receive • Initial cost to learn ways to use application, but.. • Long-term benefits offset initial costs • Faster to complete information-based task • Professional presentation

16. Expectations of Software • Negative … • Potential for lost data and/or programs • Potential for virus attacks • Rapid replacement of IT • Periodic failure • J.D.’s Law: [F <==> I * (1/R)] • the chance of computing failure (F) is proportional to the degree of importance (I) of the data times the inverse of the time remaining (R) that the data is required

17. Algorithm and Program • Algorithm • set of deterministic instructions • Program • implementation of an algorithm for a specific platform (i.e., operating system) • Abstraction vs. Representation • Data is a necessary component of each

18. Algorithm Example • Preparing Pasta and Sauce • Ingredients (like data) • Recipe (like algorithm) • Tools (like objects – defer to Ch. 5)

19. Declaration of Ingredients • fresh pasta • fresh sauce • oil • water • salt • bread • butter • garlic

20. Declaration of Tools • saucepan small • saucepan large • colander • stove • sink • set of spoons { s0 s1 ...} • tongs

21. Main Definition of Recipe 1. water into saucepan large 2. saucepan large onto stove 3. set stove heat to high 4. wait until water boils, then put pasta into water 5. wait 9 minutes, then take pasta from pot 6. put pasta into colander 7. sauce into saucepan small, then onto stove 8. set stove to medium 9. wait until sauce is hot, then remove from heat 10. place sauce on pasta

22. Recipe Issues • stove never stopped • colander drains into nowhere • sauce thru colander • no plates, table, sink • sauce pot initially high • concurrency possible if stove has 2 burners • “wait” not really defined

23. Future Expectations • Faster computing • Larger and faster access for data storage • Alternative input • Voice • Predictive • More useful output, ready to be input to another computing device • More ubiquitious

24. Implications (AE 2.4) • Diminishing Skills • Productivity • Does a PC really save time? • Does computing really save paper? • Information Technology vs. Libraries • Access capabilities • What is recorded

25. For next time … • Complete reading Chapter 2 of AE • Complete reading Chapter 10 of LoC • Begin reading Chapter 3 of AE • Attend your discussion group • Get started with Lab 0 due Feb. 7