In various articles I have read, there are sometimes references to primitive data types and sometimes there are references to scalars.
My understanding of each is that they are data types of something simple like an int, boolean, char, etc.
Is there something I am missing that means you should use particular terminology or are the terms simply interchangeable? The Wikipedia pages for each one doesn't show anything obvious.
If the terms are simply interchangeable, which is the preferred one?
null type is the only thing that most realistically conforms to the definition of a "scalar type". Even the serialization of 'None' as 'N.' fitting into a 16bit word which is traditionally scalar -- or even a single bit which has multiple possible values -- isn't a "single data".
Every primitive is scalar, but not vice versa. DateTime is scalar, but not primitive.
Being scalar has nothing to do with the language, whereas being primitive is all dependent on the language. The two have nothing to do with each other.
A scalar data type is something that has a finite set of possible values, following some scale, i.e. each value can be compared to any other value as either equal, greater or less. Numeric values (floating point and integer) are the obvious examples, while discrete/enumerated values can also be considered scalar. In this regard, boolean is a scalar with 2 discrete possible values, and normally it makes sense that true > false. Strings, regardless of programming language, are technically not scalars.
Now what is primitive depends on the language. Every language classifies what its "basic types" are, and these are designated as its primitives. In JavaScript, string is primitive, despite it not being a scalar in the general sense. But in some languages a string is not primitive. To be a primitive type, the language must be able to treat it as immutable, and for this reason referential types such as objects, arrays, collections, cannot be primitive in most, if not all, languages.
