CSC161 2010F, Class 06: Types and Operators

Overview:
* Questions and Answers.
* Hello World.
* Compiling C Programs.
* C Beyond K&R.
* Back to the Basics.
* Lab (if time permits).

Admin:
* Mostly lecture/discussion today
* I hope to respond to Assignment 1 tonight or tomorrow night.
* Are there questions on Assignment 2?
* For tomorrow, read sections 7.1-7.4 of K&R.
* Many of the examples from today's class can be found in 
  Examples/Compiling in the course web.
* EC for Charles's and Kumail's comedy on Wednesday at 8 p.m. in Harris
* Congrats to soccer!

Q&A on Chapter 2 of K&R (gathered, not necessarily answered)
* Bitwise stuff is confusing - Information coming on Friday
* Too sophisticated - Solution: Look forward to the lab in which stuff
  makes sense
* All these character constants and weird octal things and such
  * Hard to see what's important and what's just "ooh, look, you can
    do this in C"
* Why do we have a character type when characters are integers anyway?

The legendary "Hello World"
* You did a nice job of applying GNU standards

How to compile C programs in the MathLAN
* See the outline

Looking a bit beyond K&R.
* Always return from main
  0 - success
  postiive number - failure
* #include <stdlib.h>
  EXIT_SUCCESS
  EXIT_FAILURE
* #include <sysexits.h>
  (We'll look at this later.)

C Basics
* Variable Names
  * In C: sequence of letters, numbers, and underscore charactersw
    that do not begin with a number.
    OK
      hello
      l33t
      _this_variable_stores_a_really_useless_value
    Not OK
      3tt
      he-llo
      for, int, while
  * Standard: Only the first six characters are guaranteed to be 
    significant
  * Our system: At least 1000 characters are significant
* Declarations
  * Requires explicit declaration and typing
  TYPE NAME;
  int i;
  TYPE NAME1, NAME2, NAME3;
  double i, j, k;
* Assignment Statements
  VAR = EXP;
  Meaning: Evaluate the expression and shove the result in the
    memory associated with the variable.
  x = 2;
  x = x * 5;
* Primary Types
  char, int, short, long, float, double
  * All of these are FIXED-SIZE.  You can't store arbitrary numbers.
  * Need to distinguish between SIGNED (positive or negative) and
    UNSIGNED (only positive) for integer types
  * chars are just integers (small integers)
    * So why do we have them?
    * Save space (written in an era when memory was expensive)
    * We want to think of a character type, even if there's not really
      one, because it's easier to write, say 'A' than 65
* Constants
  * Way too many ways to notate.  Don't worry about anything that's
    not plain decimal right now.
* Enums
  * Your own finite type
  enum NAME { VAL1, VAL2, VAL3 };
  enum CSC161 { Radhika, Daryl, Nolen, Etc };

  enum CSC161 student_to_call_on;
  student_to_call_on = Daryl;
  student_to_call_on = 5;
  int i = Daryl;
  ++student_to_call_on;

  These values in an enum are constants, not variables

* And more?

Lab