Abstract: The present invention provides an active data type for use in a computer program. The active data type has an identifier and at least one algorithm associated therewith. The identifier is utilized by the computer program to identify the instance of the active data type. The algorithm is configured to be automatically executed when an attempt to access a value associated with the active data type instance is made by a routine or otherwise. When a particular routine that uses an instance of the active data type attempts to access the value associated with the active data type, the algorithm determines the value associated with the active data type before the routine obtains access to the value. The active data type may be a real, an integer, or a string, for example. The algorithm automatically determines the current value associated with the active data type instance. Preferably, the active data type has an identifier, a first algorithm and a second algorithm associated therewith.