When to use enums?

Question

I\'m currently reading about enums in C. I understand how they work, but can\'t figure out situations where they could be useful. Can you give me some simple examples where the

Answer 1

The concept behind an enum is also sometimes called an "enumerated type". That is to say, it's a type all of whose possible values are named and listed as part of the definition of the type.

C actually diverts from that a bit, since if a and b are values in an enum, then a|b is also a valid value of that type, regardless of whether it's listed and named or not. But you don't have to use that fact, you can use an enum just as an enumerated type.

They're appropriate whenever you want a variable whose possible values each represent one of a fixed list of things. They're also sometimes appropriate when you want to define a bunch of related compile-time constants, especially since in C (unlike C++), a const int is not a compile-time constant.

I think that their most useful properties are:

1) You can concisely define a set of distinct constants where you don't really care what the values are as long as they're different. typedef enum { red, green, blue } color; is better than:

#define red   0
#define green 1
#define blue  2

2) A programmer, on seeing a parameter / return value / variable of type color, knows what values are legal and what they mean (or anyway knows how to look that up). Better than making it an int but documenting "this parameter must be one of the color values defined in some header or other".

3) Your debugger, on seeing a variable of type color, may be able to do a reverse lookup, and give red as the value. Better than you looking that up yourself in the source.

4) The compiler, on seeing a switch of an expression of type color, might warn you if there's no default and any of the enumerated values is missing from the list of cases. That helps avoid errors when you're doing something different for each value of the enum.