C++ Programming: Language Keywords

ISO C++ keywords

The C++98 standard recognized the following keywords:

and and_eq asm auto bitand bitor bool break case catch char class compl const const_cast continue default delete do

double dynamic_cast else enum explicit export extern false float for friend goto if inline int long mutable namespace new

not not_eq operator or or_eq private protected public register reinterpret_cast return short signed sizeof static static_cast struct switch template

this throw true try typedef typeid typename union unsigned using virtual void volatile wchar_t while xor xor_eq

Specific compilers may (in a non-standard compliant mode) also treat some other words as keywords, including cdecl, far, fortran, huge, interrupt, near, pascal, typeof. Old compilers may recognize the overload keyword, an anachronism that has been removed from the language.

The current revision of C++, known as C++11, added some keywords:

alignas alignof char16_t

char32_t constexpr decltype

noexcept nullptr

static_assert thread_local

C++11 also added two special words which act like keywords in some contexts, but can be used as ordinary identifiers most of the time:

• final
• override

It would be bad practice to use these as identifiers when writing new code.

The C++98 keywords auto, default, delete and using have additional or changed uses in C++11.

Some old C++98 compilers may not recognize some or all of the following keywords:

and and_eq bitand bitor bool catch compl const_cast

dynamic_cast explicit export false mutable namespace not not_eq

or or_eq reinterpret_cast static_cast template throw true try

typeid typename using wchar_t xor xor_eq

C++ reserved identifiers

Some "nonstandard" identifiers are reserved for distinct uses, to avoid conflicts on the naming of identifiers by vendors, library creators and users in general.

Reserved identifiers include keywords with two consecutive underscores (__), all that start with an underscore followed by an uppercase letter and some other categories of reserved identifiers carried over from the C library specification.

A list of C reserved identifiers can be found at the Internet Wayback Machine archived page: http://web.archive.org/web/20040209031039/http://oakroadsystems.com/tech/c-predef.htm#ReservedIdentifiers