Enumerations

Enumerations in MQL4 define a custom, limited set of data values using named constants. They introduce a new 4-byte integer-valued data type.

Syntax

enum 
  {
   
  };

is a comma-separated list of identifiers (named constants).

Value Assignment

If a named constant is not explicitly assigned a value, it is assigned automatically. The first member defaults to 0. Subsequent members increment by one from the previous member.

Explicit values can be assigned to named constants.

Example 1 (Automatic Assignment)

enum months
  {
   January, // 0
   February, // 1
   March, // 2
   April, // 3
   May, // 4
   June, // 5
   July, // 6
   August, // 7
   September, // 8
   October, // 9
   November, // 10
   December // 11
  };

Example 2 (Explicit and Automatic Assignment)

enum intervals
  {
   month=1,       // Interval of one month
   two_months,    // Two months (value 2)
   quarter,       // Three months - quarter (value 3)
   halfyear=6,    // Half a year
   year=12        // Year - 12 months
  };

Key Characteristics and Constraints

**Size:** The internal representation of any enumerated type is always 4 bytes (e.g., sizeof(months) returns 4).

**Naming:** A unique name must always be specified after the enum keyword; anonymous enumerations are not permitted (unlike C++).

**Type Safety:** Enumerations enable strict type control for function parameters, as they introduce new named constants.