Depending on the implementation and compiler
option, other specialized identifiers, such as the dollar sign ($)
or characters in national character sets, may be allowed to appear
in an identifier.The first character in an identifier must be a letter or the _ (underscore) character; however, beginning identifiers with an underscore is considered poor programming style.
The compiler distinguishes between uppercase and lowercase letters in identifiers. For example, PROFIT and profit represent different identifiers. If you specify a lowercase a as part of an identifier name, you cannot substitute an uppercase A in its place; you must use the lowercase letter.
The universal character names for letters and digits outside of the basic source character set are allowed in C++ .
Depending on the implementation and compiler
option, other specialized identifiers, such as the dollar sign ($)
or characters in national character sets, may be allowed to appear
in an identifier.