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Enumerated Type

Overview​

An Enumerated type (Enum) is a data type that defines a fixed set of named values. Each value represents a distinct, meaningful constant, making programs easier to read, safer, and less error-prone.

Enums replace mysterious numbers with self-explanatory names.

What Is an Enumerated Type?​

An enum:

  • Contains a finite list of identifiers
  • Each identifier maps to a constant value
  • Restricts variables to valid, predefined options

Only the declared values are allowed.

How It Works​

Internally, enum values are often stored as integers, but externally they behave as named constants.

Example mapping:

RED   → 0
GREEN → 1
BLUE  → 2

The mapping is usually hidden from the programmer.

Enum vs Constants​

AspectEnumConstants
Type safetyYesNo
Value restrictionEnforcedNot enforced
ReadabilityHighMedium
NamespaceScopedGlobal

Common Operations​

  • Assignment
  • Comparison
  • Iteration over values
  • Conversion to/from integers or strings

Example​

Pseudocode​

enum Status { NEW, PROCESSING, DONE }

taskStatus = Status.NEW

if taskStatus == Status.DONE:
    archiveTask()

Real-world Analogy​

An enum is like a menu with fixed choices. You can order anything on the list, but nothing off-menu 🍽️.

Time and Space Complexity​

  • Space: O(1)
  • Comparison: O(1)

Use Cases​

  • State machines
  • Configuration options
  • Finite categories
  • Error codes
  • Protocol definitions

Advantages​

  • Prevents invalid values
  • Improves code readability
  • Easier maintenance

Limitations​

  • Fixed at compile time
  • Not suitable for dynamic sets
  • Limited extensibility