Objective-C Fundamentals

294 APPENDIX B The basics of C
compiler or support libraries. Identifiers can be of any length but are case sensitive,
so fooBar, FOOBAR, and FooBar are all valid identifiers that refer to different items in
an application.
Following are some examples of valid variable identifiers:
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MyVariable
variable123
Another_Variable
And here are some examples of invalid variable identifiers:
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$Amount
cost(in_cents)
monthly rental
10timesCost
int
The last invalid variable identifier, int, deserves additional comment. At first glance,
it may appear to pass all the rules for valid identifiers. The keyword int, however,
already has a special meaning in C source code. It identifies the integer primitive data
type. Keywords that already have a special meaning in a C application are called
reserved words. A reserved word is an identifier that has a special meaning to the C compiler
and therefore can’t be used as an identifier in your source code. Other examples
of reserved words include if, return, and else, among others.
B.1.1
Hungarian notation
Although you’re free to name your variables using any identifier that conforms to the
rules previously specified, over the years a number of traditions and conflicting styles
have developed regarding the best way to name identifiers. Many developers already
familiar with C-based applications are aware of a convention called Hungarian notation.
Hungarian notation is the concept of encoding into your variable names a description
of the data type associated with the variable. This is done via a prefix that represents
the data type; for example, iCount indicates an integer count, and chGender
indicates a variable capable of storing a character. Table B.1 lists some of the most
common prefixes you may encounter.
Table B.1
Common Hungarian notation prefixes for variable names in C source code
Example variable identifiers
Description
chFoo
iFoo, nBar, cApples
bFlag, fBusy
Character (char)
Integer, number or count (int)
Boolean or flag (BOOL)
pszName Pointer to null terminated string (char *)