Type system
set of rules that assign a property called type to various constructs a computer program consists of, such as variables, expressions, functions or modules
A programming language consists of a system of allowed sequences of symbols (constructs) together with rules that define how each construct is interpreted. For example, a language might allow expressions representing various types of data, expressions that provide structuring rules for data, expressions representing various operations on data, and constructs that provide sequencing rules for the order in which to perform operations.
A simple type system for a programming language is a set of rules that associates a data type (for example, integer, floating point, string) with each term (data-valued expression) in a computer program. In more ambitious type systems, a variety of constructs, such as variables, expressions, functions, and modules, may be assigned types.
Type systems formalize and enforce the otherwise implicit categories the programmer uses for algebraic data types, data structures, or other data types, such as "string", "array of float", "function returning boolean".
The main purpose of a type system in a programming language is to reduce possibilities for bugs in computer programs due to mismatches in how values are interpreted in different parts of a program. The aim is to prevent operations expecting a certain kind of value from being applied to values for which that operation does not make sense (validity errors). A type system can detect and prevent some of these mismatches. When a type mismatch is detected, it is called a type error.
The type of a term constrains the contexts in which it may be used.
This brief starts where responsible research should: with the source description of “Type system” as set of rules that assign a property called type to various constructs a computer program consists of, such as variables, expressions, functions or modules. Everything that follows is an evidence route, not borrowed authority.
Why this record matters
The subject matters to the general reference register because the source frames it as set of rules that assign a property called type to various constructs a computer program consists of, such as variables, expressions, functions or modules. Its deeper value depends on whether names, dates, institutions and citations support that framing.
Named sources, stable identifiers and responsible institutions provide the strongest route from overview to verifiable evidence. The source revision retrieved here is dated Aug 23, 2026. The linked authority identifier is Q865760. None of the 0 selected statements returned an explicit reference.
Overview language is designed for orientation and should not be treated as a substitute for the evidence cited beneath it. The source lead contains qualifying language; that uncertainty should survive quotation, summary and reuse. Authority statements aid reconciliation but still require their own references, qualifiers and ranks to be checked.
How to read it
Use the entry as an orientation point, then follow its citations and revision history. Names, dates and institutional relationships should be checked against the original record.
- Subject orientation
- Search vocabulary
- Locating named sources
The closest primary source, responsible institution and strongest cited specialist reference.
Three-step research path
- Establish the record: confirm the title “Type system”, its source revision and the description used here.
- Expand the search: follow Type system primary sources, Type system archive and Type research across catalogues and specialist indexes.
- Test the account: compare the strongest cited source with the responsible institution’s current record and note any disagreement.
Questions for further research
- Which source most directly establishes the central claim about “Type system”?
- Which institution is responsible for the underlying evidence?
- Which cited source is closest to the event, object or claim?
Search terms from this dossier
This entry incorporates text from “Type system” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.