Naming Conventions (Hungarian)

Term Paper Title	Naming Conventions (Hungarian)
# of Words	8153
# of Pages (250 words per page double spaced)	32.61

Naming Conventions (Hungarian)

Doug Klunder
January 18, 1988
1.     Introduction

This document describes a set of naming conventions used by the Applications Development group. These conventions commonly go by the name "Hungarian", referring both to the nationality of their original developer, Charles Simonyi, and also to the fact that to an uninitiated programmer they are somewhat confusing. Once you have gained familiarity with Hungarian, however, we believe that you will find that the clarity of code is enhanced. For convenience, this memo first describes how to use Hungarian, and then describes why it is useful; the general approach is from a programming viewpoint, rather than a mathematical one. For a more theoretical approach, you are invited to read Chapter 2 of Simonyi's "Meta-Programming" thesis.
2.     The Rules
Hungarian is largely language independent; it is equally applicable to a microprocessor assembly language and to a fourth-generation database application language (and has been used in both). However, there is a little flavor of C, in that arrays and pointers to arrays are not clearly distinguished. While this may sound confusing, in practice there is little ambiguity.
2.1.     Variables
The most common type of identifier is a variable name. All variable names are composed of three elements:  prefixes, base type, and qualifier. (These are also referred to as constructors, tag, and qualifier). Not all elements are present in all variable names; the only part that is always present is the base type. This type should not be confused with the types supported directly by the programming language; most types are application specific. For example, an lbl type could refer to a structure containing symbol information; a co could be a value specifying a color.
2.1.1.     Base types (tags)
As the above examples indicate, tags should be short (typically two or three letters) and somewhat mnemonic. Because of the brevity, the mnemonic value will be useful only as a reminder to someone who knows the application, and has been told what the basic types are; the name will not be sufficient to inform (by itself) a casual viewer what is being referred to. For example, a co could just as easily refer to a geometric coordinate, or to a commanding officer. Within the context of a given application, however, a co would always have a specific meaning; all co's would refer to the same type of object, and all references to such an object would use the term co.
One should resist the natural first impulse to use a short descriptive generic English term as a type name. This is almost always a mistake. One should not preempt the most useful English phrases for the provincial purposes of any given version of a given program. Chances are that the same generic term could be equally applicable to many more types in the same program. How will we know which is the one with the pretty "logical" name, and which have the more arbitrary variants typically obtained by omitting various vowels or by other disfigurement? Also, in communicating with other programmers, how do we distinguish the generic use of the common term from the reserved technical usage? In practice, it seems best to use some abbreviated or form of the generic term, or perhaps an acronym. In speech, the tag may be spelled out, or a pronounceable nickname may be used. In time, the exact derivation of the tag may be forgotten, but its meaning will still be clear.
As is probably obvious from the above, it is essential that all tags used in a given application be clearly documented. This is extremely useful in helping a new programmer learn the code; it not only enables him (or her) to decode the otherwise cryptic names, but it also serves to describe the underlying concepts of the program, since the data types tend to determine how the program works. It is also worth pointing out that this is not nearly as onerous as it sounds; while there may be tens of thousands of variables in a program, the number of types is likely to be quite small.
Although most types are particular to a ...

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