CSC151, Class 38: Files

Overview:
* Review of I/O
* Short introduction to files
* Lab

Notes:
* Exam 2 due.
* Project proposals assigned
* One point of extra credit for attending "Global Communication
  Technologies and Cultural Exchange", 8pm, Forum South Lounge.
* Goldenbergs almost gone.

What did you learn yesterday?
* I can input and output things in Scheme.
  Side note: William likes to gamble
* Why is this a useful thing to do?
  Write programs that interact with people?
* Another reason: These operations can be used to save information
  from a program to a file and later read that information back
  in.
* Note: If you're reading from (or writing to) a file you
  need to know where in the file you are.
* Detour: What is a file?
  A collection of information stored on the hard drive of
  one or more computers.
  It's up to you as programmer/computer user to decide
  what goes in what file.
* Where should you normally write to a file?
  After the last thing you wrote.
* Sometimes we want to overwrite.
* In Scheme, you convert files to PORTS which have a notion
  as to where is the next place in the file

REFLECTION

* Sometimes Sam's mind takes odd paths:
  Class observe's Sam pausing for no clear reason.
  "Computer user" 
  -> "I don't like the word user." 
  -> "Why not?"
  -> "Um ... maybe because it sounds like 'drug user'."
  -> "Oh yeah!  Special on Crank on HBO tonight."
       "Welcome to Des Moines, Iowa, Small town midwest"

* How did you verify sum-of-file?

* How did you you write size-of-file?

* Did anyone other than Povilas try local kernels?

'Twas brillig and the slithy toves
  did gyre and gimble in the wabe
All mimsy were the borogoves
  and the mome raths outgrabe.

"Beware the Jabberwock, my son,
  the jaws that bite, the claws that catch.
Beware the jubjub bird 
  and shun the frumious bandersnatch."

He took his vorpal sword in hand.
  Long time the manxome foe he sought.
So rested he by the tumtum tree,
  and stood awhile in thought.

And as, in uffish thought he stood,
  the Jabberwock with eyes of flame
Came whiffling through the tulgey wood
  and burbled as it came.

One.  Two.  One. Two.  And through and through.
  The vorpal blade went snicker-snack.
He left it dead and with its head
  he went galumphing back.

"And hast thou slain the Jabberwock?
  Come to my arms, my beamish boy!
Oh frabjuous day!  Callou!  Callay!"
  he chortled in his joy.

'Twas brillig and the slithy toves
  did gyre and gimble in the wabe
All mimsy were the borogoves
  and the mome raths outgrabe.