Hungarian Notation is mainly confined to Microsoft Windows programming environments, such as Microsoft C, C++ and Visual Basic. It was originally devised by Charles Simonyi, a Hungarian, who was a senior programmer at Microsoft for many years. Hungarian notation involves storing information about the variable in the very name of the variable. Information such as the data type and variable scope can usually be inferred by looking at the name of the variable. With Hungarian notation, variable names are separated into two parts:
The lowercase prefix, which contains information about the variable type, and
The qualifier, which tells you what the variable contains. The qualifier usually begins with a capital letter.
For example: pstrError
This would be a pointer to a string, and which will contain an error message.
Most of the Windows API, code samples and documentation are written in this notation. Please note that the Hungarian notation is something developed for the C language and not the C++. In C, it is quite simple to come up meaningful prefixes for the "few" types, which make sense in a particular domain (like Windows programming). With C++, it is really more difficult situation.
Hungarian Notation is not really necessary when using a modern strongly-typed language as the compiler warns the programmer if a variable of one type is used as if it were another type. It is less useful in object-oriented programming languages such as C++, where many variables are going to be instances of classes.
CamelCase notation is a common name for the practice of writing compound words or phrases where the words are joined without spaces, and each word is capitalized within the compound. This practice is known by a large variety of names, including BiCapitalization, InterCaps, MixedCase, etc. CamelCase is a standard identifier naming convention for several programming languages and also has become fashionable in marketing for names of products and companies. The CamelCase name comes from the uppercase "bumps" in the middle of the compound word, suggesting the humps of a camel. For example:
There are two common varieties of CamelCase, distinguished by their handling of the initial letter. The variety in which the first letter is capitalized is commonly called UpperCamelCase, PascalCase, or BiCapitalized. The variety in which the first letter is left as lowercase is commonly called lowerCamelCase or sometimes simply camelCase. The term StudlyCaps is similar but not necessarily identical to CamelCase. It is sometimes used in reference to CamelCase but can also refer to random mixed capitalization (as in "MiXeD CaPitALiZaTioN") as popularly used in online culture. Other synonym examples for CamelCase notation include:
mixedCase (for lowerCamelCase) in Python (reference)
ClCl (Capital-lower Capital-lower) and sometimes ClC
WordsStrungTogether or WordsRunTogether
In programs of any significant size, there is a need for descriptive (hence multi-word) identifiers, like "previous balance" or "end of file". Writing the words together as in "endoffile" is not satisfactory because the names often become unreadable. ASCII character set standard that had been established by the late 1960s, allowing the designers of the C language to adopt the underscore character "_" as a word joiner. Underscore-separated compounds like "end_of_file" are still prevalent in C programs and libraries.
As programs have become more complex both in terms of size and of the proliferation of data types, many programmers have adopted a variable-naming convention, which is commonly referred to as Hungarian notation (apocryphally named in honor of Microsoft programmer, Charles Simonyi). Another notation commonly used in programming language is CamelCase.
Over the past several years, several standard versions of Hungarian notation have been proposed and/or published. The version given here is dictated in part by personal preferences and in part by conventions established by Windows in naming constants, variable, and data structure definitions. Because all of these standards are intended to be mnemonic for your convenience, you may follow or alter them as desired. Using Hungarian notation, variable names begin with one or more lowercase letters that denote the variable type, thus providing an inherent identification. For example, the prefix h is used to identify a handle, as in hWnd or hDlg, referring to window and dialog box handles, respectively. In similar fashion, the prefix lpsz identifies a long pointer to a null-terminated (ASCIIZ) string. Table 1 summarizes some of the Hungarian notation conventions.
byte or unsigned char.
cx / cy
short used as size.
DWORD, double word or unsigned long.
a pointer variable containing the address of a variable.
ASCIIZ null-terminated string.
WORD unsigned int.
short used as coordinates.
Table 1: Hungarian Notation Convention examples.
Windows also uses an extensive list of predefined constants that are used as messages, flag values, and other operational parameters. These constant values are always full uppercase and most include a two- or three-letter prefix set off by an underscore. Here are some examples:
In the case of constant identifiers, the prefixes indicate the general category of the constant. Table 2 shows the meanings of the prefixes in the examples shown here.
Table 2: A Few Constant Prefixes.
Windows also uses a wide variety of new data types and type identifiers, most of which are defined in either the WinDef.H or WinUser.H header files. Table 3 lists a few of the more common data type examples.
Same as far. Identifies an address that originally used the segment:offset addressing schema. Now FAR simply identifies a (default) 32-bit address but may be omitted entirely in many cases.
Same as Pascal. The Pascal convention demanded by Windows defines the order in which arguments are found in the stack when passed as calling parameters.
Unsigned integer (16 bits)
Unsigned integer, same as WORD
Double word, unsigned long int (32 bits)
Signed long integer (32 bits)
Long (far) pointer to character string
Obsolete, previously identified an address value within a 16KB memory block.
Table 3: A Few Windows Data Types.
Similarly, Windows adds a variety of new data structures. Again, most are defined in either WinDef.H or WinUser.H. The examples shown in Table 4.
Point structure (mouse position).
Rectangle structure, two coordinate pairs.
Window class structure.
Table 4: Examples of notation used for Windows structures.
In like fashion, a variety of handles are defined for use with different Windows elements. Like constants, the handle types use all uppercase identifiers. Table 5 shows a few examples.
hnd or hdl
hwnd or hWnd
hdc or hDC
Device-context handle (CRT)
hbr or hBrush
Paint brush handle
hpen or hPen
Drawing pen handle
Table 5: Five Handle Identifiers.