[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 ([dcl.attr.grammar]).

[Note 1:

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]

5.12 Keywords [lex.key]