CSC151 2007S, Class 22: Input and Ouptut

Admin:
* Homework 8 is now due Friday.
* Homework 9 is now due Friday.
* Questions on either homework?
* Reading for tomorrow: Files
* Convo Thursday: Jackie Brown
* CS Extra Thursday: Google(R)'s PageRank(R) algorithm
  * Noon (I think)
  * Requires understanding of linear algebra (I think)

Overview:
* Interactive programs.
* Output in Scheme.
* Input in Scheme.
* lab

/Context: What does it mean to work with a program?/

* In Scheme: Type expression in interactions pane and seeing it compute a result
* Current model: WIMP: Windows, Icons, Menus, Pointers
  * Behind the scenes, these actions "Click here", "Type here" are
    turned into input for a program
* Interactive terminal model: Type something (in response to a prompt), 
  see a resopnse
* Batch model: Submit program and input.  Wait.  Wait. Wait.  Get some
  tea (not in a plastic cup which will probably melt in the microwave).
  See the results.
 
/Scheme Supports the Interactive Terminal Model/

* um (corresponds to "wait some more")
* display - one of the ways to show output - Human readable
* read - get the next input value
* write - another way to show output - Scheme readable
* newline - moves on to the next line of text (underneath the current line)