CSC151 2010S, Class 01: An Introduction to Algorithms

Overview:
* Introduction: What is CS?
* Exercise: An everyday algorithm.

Admin:
* Welcome to 151.
* The Course Web site will be in a bit of flux for the first few days.
* I will take attendance for the first few days, but I will probably take 
  a month to attach names to faces and perhaps longer to learn to pronounce 
  names correctly.
* Two assignments for Tuesday: (sorry about the incorrect date)
  (1) Take the introductory survey; 
  (2) Read "Grinnell's Linux Environment" (available online).

What is Computer Science?

* Understanding the language of computers
  * Further question: What's a computer?
  * The language may be inscrutable and involve 
    lots of brackets and weird acronyms
* A computer is a device that takes input
  * Some of that input is instructions
  * The computer uses those instructions to 
    process that input
  * It usually then outputs the result of that processing
* A computer is something that computes
* Flaws to that definition:
  * Doesn't really describe the hardware of the 
    computer
  * Is a definition of something in terms of what 
    it does a reasonable definition?  Yes.
* Okay, we know what a computer is.  What is
  *computer science*?
  * Study of methods of computation
    * Because "science" means "study"
  * Scientific method is fun and systematic way to 
    study the world
    * Observe or read literature, make hypotheses, experiment (repeatable), analyze, conclude, (and refine hypothesis)

Possible hypothesis: I can use my computer to do X if I do Y.
* Refined: A set of instructions (an "algorithm") will accomplish a particular task
* Of course, mathematicians would suggest that you analyze the instructions differently: proof

A lot of what computer scientists do is work with algorithms and data structures (ways of organizing data)
* Design them
* Write them in a particular language
* Study the algorithms we or others have written
  * For correctness
  * For efficiency
  * (For elegance)
* Consider the effects

This is a class about writing algorithms!
* So let's write one

Debriefing today and tomorrow
* What did you learn from this exercise?
  * You may need to explain everything!
* It helps to have some knowledge of what the
  computer knows and how the computer processes
* The first algorithm is rarely perfect.  Be
  prepared to correct flaws
  * And try to predict errors
* Details are helpful
* It's helpful to try each part as you go and to
  correct
* You can only use the particular inputs the 
  computer recognizes

* IT'S REALLY FUNNY WHEN THINGS GO WRONG!