What is the difference between enumeration and set of preprocessor define in c?

Answer 1

An enumeration is a group of named integral constants. An enumeration is also a type thus it provides type safety. When passing a constant to a function, an enumeration eliminate values that are not part of the group, thus allowing the compiler to catch errors that would otherwise slip through.

A set or pre-processor definitions (or macro definitions) do not provide any type safety and are never actually seen by compiler (they are processed before the compiler sees the resultant code). Macros are nothing more than a text-replacement system that effectively allow programmers to create a language within the programming language and thus create code that would be difficult if not impossible to produce using the language alone. However, when the language provides a simpler, type-safe mechanism, it is always better to utilise it and thus enlist the help of the compiler to eliminate errors. Macros do have their uses, particularly when debugging, but they must be used only when it is appropriate to do so. Enumerations are preferred over a set of macro definitions every time.

Some languages also permit enumeration classes, which gives stronger guarantees than a "plain" enumeration, not least eliminating the implicit promotion between enumerated types and integral types.

Answer 2

Enums are compile time substituted constants whereas #defines are preprocessing substituted time constants