5. Other type systems

Dynamic typing, by checking that the arguments passed to a function are of the correct type, ensures that the operations performed are carried out on the correct type of data. To achieve this, tests on the data passed are carried out before a function is called, or directly in its code. If one of these type conformity tests fails, this is signalled either by passing a specific value to the caller, or by triggering an exception at that point in the program. The result is a software reliability guarantee that calculations will not be performed on data that does not conform to expectations.

Static typing eliminates typing tests at runtime by analyzing the program's source code to check that it conforms to the type system of the language in which the program is written. If this is not the case, the program will not be compiled and therefore cannot be executed. If this...