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2. Software Applications CS100: The World of Computing John Dougherty Haverford College Outline of Presentation Hardware vs. Software Expectations of Software Algorithm Example Limits Future Expectations Implications Hardware Tangible – anything you can touch Devices and components used in computing Examples Computer Disk Mouse Printer Cables Software Intangible – “can’t touch this” Examples Programs Operating System Applications Data Ideas ? Emotions ? 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 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 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 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 Application Development a.k.a,. software engineering Typically a coordinated team effort Specification Design Implementation Testing Maintenance 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 Data Often considered the inert part of software Used to hold information for computing Numeric Alphabetic Graphic Audio Data and Hardware Stored on … Floppy disk RAM (Random Access Memory) CD-ROM DVD Tape Paper ? “… like music is to an instrument, …” 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) 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)) 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 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 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 Algorithm Example Preparing Pasta and Sauce Ingredients (like data) Recipe (like algorithm) Tools (like objects – defer to Ch. 5) Declaration of Ingredients fresh pasta fresh sauce oil water salt bread butter garlic Declaration of Tools saucepan small saucepan large colander stove sink set of spoons { s0 s1 ...} tongs 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 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 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 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 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