Typesmajor

Typesmajor is a conceptual framework used in programming language theory to classify data types by their primary semantic role within a type system. The central idea is to identify a set of major type categories that organize how values are stored, referenced, or executed, with additional minor type distinctions that refine behavior such as mutability, ownership, or effects. The term emphasizes the distinction between the broad kind of value and the more specific traits that govern its use at compile time.

In typical formulations, major types include data or value types, reference or pointer types, and function or callable types. Some approaches also treat effectful types, which model computations that interact with the outside world, as a distinct major category. Value types denote concrete data that can be stored and copied, such as integers or records. Reference types represent pointers or aliases to data stored elsewhere, influencing access patterns and aliasing. Function types describe executable code that can be passed as values or invoked. Effect types capture side effects like I/O or state changes and often require separate handling in the type system.

Minor types accompany major types to express finer properties. Common refinements include mutability (mutable vs immutable), ownership or borrowing constraints, lifetime or scope, and concurrency-related restrictions. The interplay between major and minor types supports reasoning about memory safety, aliasing, and cross-language interoperability.

Typesmajor serves as a design tool for language architects and researchers, helping to map type-system goals to concrete rules. It is not universally adopted, but it provides a vocabulary for discussing broad categories of types and their interactions. See also type theory, memory safety, ownership types.