[lex.key]

The identifiers shown in Table 5 are reserved for use as keywords (that is, they are unconditionally treated as keywords in phase 7) except in an attribute-token .

[Note

The register keyword is unused but is reserved for future use.

— end note

]

Table 5: Keywords [tab:lex.key]

alignas	constinit	false	public	true
alignof	const_cast	float	register	try
asm	continue	for	reinterpret_cast	typedef
auto	co_await	friend	requires	typeid
bool	co_return	goto	return	typename
break	co_yield	if	short	union
case	decltype	inline	signed	unsigned
catch	default	int	sizeof	using
char	delete	long	static	virtual
char8_t	do	mutable	static_assert	void
char16_t	double	namespace	static_cast	volatile
char32_t	dynamic_cast	new	struct	wchar_t
class	else	noexcept	switch	while
concept	enum	nullptr	template
const	explicit	operator	this
consteval	export	private	thread_local
constexpr	extern	protected	throw

Furthermore, the alternative representations shown in Table 6 for certain operators and punctuators ([lex.digraph]) are reserved and shall not be used otherwise.

Table 6: Alternative representations [tab:lex.key.digraph]

and	and_eq	bitand	bitor	compl	not
not_eq	or	or_eq	xor	xor_eq

5 Lexical conventions [lex]

5.11 Keywords [lex.key]