CSC195, Class 13: Fundamental Types in C

Overview
* What is a type?
* Integer types
* Floating-point types
* Other key types
* Enumerated types
* Key numeric operations
* Lab

Notes
* Take-home exam next week

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What is a type?
* A mechanism for converting sequences of 0's and 1's to
  other kinds of values.
  + As such, it speaks to the amount of space a value takes.
* A type is a set of values
* A type is a set of restrictions on when a value can be used
  in an expression
  + Conversely, it's a set of capabilities that suggest when
    the value can be used.
  + When can I call (sqrt x)
  + Why we usually type values

* Inverse of anti-type
* A type is a distinguishable type of object
* How do you define a set without enumerating the values?
  Recursively and with other set operations

Languages typically provide different kinds of types
* Primitive types (directly correspond to bit patterns)
* Mechanisms for building compound types (e.g., records,
  classes) from types
* Mechanisms for naming types

Primitive Types in C: Primarily Numeric
* Integers
  int
  unsigned int
  short int (also just "short")
  unsigned short int
  long int (also just "long")
  unsigned long int
  long long int
* Very few specifications on size
* Floating Point Numbers
  float
  double
  long float
* No specification on size (in spite of names)
* No specification on encoding

Other basic types are essentially integers
* char: just integers (typically one byte)
* boolean: just integers (typically int size)

Simplest user-defined types: enumerated types

enum day { MONDAY, TUESDAY, WEDNESDAY, THURSDAY, FRIDAY, 
           SATURDAY, SUNDAY };

Why bother?
* Programs can be easier to read and understand.
"int x" vs "enum day x"
"x = 2" vs "x = WEDNESDAY"

Operations: All the ones you expect.
  ++b vs. b++

for (i = 0; i < 10; ++i)
  vs.
for (i = 0; i < 10; i++)

Only matters if in an assignmetn, procedure call, or argument
to an operator

C++

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x += exp
  EValuate exp, increment x by that value
x *=
  =+

x=+2  <- Ambiguous

a = b++ - b++

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* The smallest unsigned integer of any kinds is 0 (ZERO)

* You'll need to choose the right parameter for printf, E.g.,
  printf("%u\n", UINT_MAX);

* Write a little, test a little, write a little, test a little.