1. Enumeration Types and typedef

2. enum Used to declare enumeration types.
Allows to name a finite set and to declare identifiers, called enumerators.

3. Creates the user-defined type enum day. tag name
constants of type int
enum day {sun, mon, tue, wed, thu, fri, sat};
enum day d1, d2; …
d1 = fri;
if (d1 == d2) 1 6

4. Enumerators can be initialized.
We can declare variables directly after the enumerator declaration.
enum suit {clubs = 1, diamonds, hearts, spades} a, b, c; 2 3 4
enum fruit {apple = 7, pear, orange = 3, lemon} frt; 8 4

5. It is allowed, but the identifiers must be unique.
enum veg {beet = 17, corn = 17} vege1, vege2;
It is allowed, but the identifiers must be unique.
enum {fir, pine} tree;
The tag name need not be present. But no other
variables of type enum {fir, pine} can be declared.

6. typedef An identifier can be associated with a specific type.
typedef int color;
color red, blue, green;
The typedef facility allows the programmer to use type names that are appropriate for a specific application. Also, helps to control complexity when programmers are building complicated or lengthy user-defined types.

7. Example – Compute the next day
enum day {sun, mon, tue, wed, thu, fri, sat};
typedef enum day day;
day find_next_day(day d) {
day next_day;
switch (d) {
case sun:
next_day = mon;
break;
tag name
type

8. case mon:
next_day = tue;
break; …
case sat:
next_day = sun; }
return next_day;

9. Another Version cast enum day {sun, mon, tue, wed, thu, fri, sat};
typedef enum day day;
day find_next_day(day d) {
return((day) (((int) d + 1)%7)); }
cast

10. Style
Enumerators can be mnemonic. => Their use tends to be self-documenting.
The use of enumeration types is considered good programming style.
enum bool {false, true};
enum off_on {off, on};
enum no_yes {no, yes}
enum speed {slow, fast}
Put such declarations
in header files.
(good programming
style)

11. Style All acceptable. Which one is used is a matter of personal taste.
enum lo_hi {lo, hi};
typedef enum lo_hi lo_hi;
All acceptable.
Which one is
used is a
matter of
personal taste.
typedef enum lo_hi {lo, hi} lo_hi;
typedef enum {lo, hi} lo_hi;