Hungarian notation

Hungarian notation is an identifier naming convention in computer programming, in which the name of a variable or function indicates its intention or kind, and in some dialects its type. The original Hungarian Notation uses intention or kind in its naming convention and is sometimes called Apps Hungarian as it became popular in the Microsoft Apps division in the development of Word, Excel and other apps. As the Microsoft Windows division adopted the naming convention, they used the actual data type for naming, and this convention became widely spread through the Windows API; this is sometimes called Systems Hungarian notation.

Simonyi: ...BCPL [had] a single type which was a 16-bit word... not that it matters.

Booch: Unless you continue the Hungarian notation.

Simonyi: Absolutely... we went over to the typed languages too later ... But ... we would look at one name and I would tell you exactly a lot about that...

Hungarian notation was designed to be language-independent, and found its first major use with the BCPL programming language. Because BCPL has no data types other than the machine word, nothing in the language itself helps a programmer remember variables' types. Hungarian notation aims to remedy this by providing the programmer with explicit knowledge of each variable's data type.

In Hungarian notation, a variable name starts with a group of lower-case letters which are mnemonics for the type or purpose of that variable, followed by whatever name the programmer has chosen; this last part is sometimes distinguished as the given name. The first character of the given name can be capitalized to separate it from the type indicators (see also CamelCase). Otherwise the case of this character denotes scope.

The original Hungarian notation, which would now be called Apps Hungarian, was invented by Charles Simonyi, a programmer who worked at Xerox PARC circa 1972–1981, and who later became Chief Architect at Microsoft.

The name of the notation is a pun on the idiom "It's all Greek to me" and uses a reference to Simonyi's nation of origin. In addition, Hungarian people's names are "reversed" compared to most other European names; the family name precedes the given name. For example, the anglicized name "Charles Simonyi" in Hungarian was originally "Simonyi Károly". In the same way the type name precedes the "given name" in Hungarian notation rather than the more natural, to most Europeans, Smalltalk "type last" naming style e.g. aPoint and lastPoint. This latter naming style was most common at Xerox PARC during Simonyi's tenure there.

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