Editing Program analysis (section)

=== Type systems ===
{{main|Type system}}
Type systems associate types to programs that fulfill certain requirements. Their purpose is to select a subset of programs of a language that are considered correct according to a property.

* [[Type_system#Type_checking|Type checking]] – verify whether the program is accepted by the type system.

Type checking is used in programming to limit how programming objects are used and what can they do. This is done by the compiler or [[interpreter (computing)|interpreter]]. Type checking can also help prevent vulnerabilities by ensuring that a signed value isn't attributed to an unsigned variable.
Type checking can be done statically (at compile time), dynamically (at runtime) or a combination of both.

Static type information (either [[type inference|inferred]], or explicitly provided by type annotations in the source code) can also be used to do optimizations, such as replacing [[boxed type|boxed arrays]] with unboxed arrays.