Lecture 18 - Types, Type Qualifiers, Storage Classes, C Preprocessor

Question 1

types (and what basic ones are called)

Answer 1

• there are many basic types in the C language
• they are called first class types
• void, char, short, int, long, long long, float, double

Question 2

sizes of data

Answer 2

• there are general rules of thumb for the size of a variable, depending on type (use sizeof() to be sure)
• ex. rules that say an int must be no smaller than a short or larger than a long
• types are automatically promoted to the next larger type of the same family within arithmetic operations

Question 3

conversion

Answer 3

• after promotion, arguments to an operator are checked
• if the same, proceed, otherwise conversions may take place
• for each type, if one of the arguments is that type, the other is converted to the same type

Question 4

type modifiers

Answer 4

• integer types (char, short, int, long, long long) can have an additional modifier to indicate to the compiler whether the datum represent a signed or unsigned (always positive) value
• for not-integer types, “signed” has no meaning
• the default modifier for int is signed

Question 5

second-class types

Answer 5

• constructed types are second class types made by the programmer
• ex. include struct, union, enum, or pointer to anything

Question 6

assignments

Answer 6

• you can make assignments between compatible types or types that can be promoted
• usually works between all first class types
  ex.
  int i;
  unsigned int ui;
  float f;
  char c;
  …
  f = ui;
  i = f;
  c = f;

Question 7

bad assignments

Answer 7

• can’t make assignments between data of differing second-class types
• ex. can’t make it between the structs my_struct and your_struct

Question 8

type qualifiers

Answer 8

• there are two type qualifiers that can be used with any type declaration
• const: this datum must not be modified
  -volatile: this datum may be modified by something outside the program
• only one at a time may be used for any single declaration

Question 9

const pointers

Question 10

const pointer arguments

Question 11

cost pointer examples

Question 12

storage classes

Question 13

when to user extern

Question 14

two modules

Question 15

static local variable

Question 16

static global variables

Question 17

why do we use any of these?