C++ Keywords

Last Updated : 23 Dec, 2024

Keywords are the reserved words that have special meanings in the C++ language. They are the words that the language uses for a specifying the components of the language, such as void, int, public, etc. They can’t be used for a variable name or function name or any other identifiers.

Let’s take a look at the hello world code:

C++

#include <iostream>
using namespace std;

int main() {
  
    cout << "Hello World";
  
    return 0;
}

Output

Hello World

Explanation: In the above code, using, namespace, and return are the keywords that are used to implement some functionality of the language. Their meaning is predefined in C++ and will always remain same.

The total number of keywords in C++ are 95 upto C++ 23 specification. Below is the table for all C++ keywords:

alignas	alignof	and	and_eq	asm
auto	bitand	bitor	bool	break
case	catch	char	char8_t	char16_t
char32_t	class	compl	concept	const
consteval	constexpr	constinit	const_cast	continue
co_await	co_return	co_yield	decltype	default
delete	do	double	dynamic_cast	else
enum	explicit	export	extern	false
final	float	for	friend	goto
if	inline	int	long	mutable
namespace	new	noexcept	not	not_eq
nullptr	operator	or	or_eq	private
protected	public	register	reinterpret_cast	requires
return	short	signed	sizeof	static
static_assert	static_cast	struct	switch	template
this	thread_local	throw	true	try
typedef	typeid	typename	union	unsigned
using	virtual	void	volatile	wchar_t
while	xor	xor_eq

Keywords vs Identifiers

So, there are some properties of keywords that distinguish keywords from identifiers. They listed in the below table

Keywords	Identifiers
Keywords are predefined/reserved words	identifiers are the values used to define different programming items like a variable, integers, structures, and unions.
It defines the type of entity.	It classifies the name of the entity.
A keyword contains only alphabetical characters,	an identifier can consist of alphabetical characters, digits, and underscores.
It should be lowercase.	It can be both upper and lowercase.
No special symbols or punctuations are used in keywords and identifiers.	No special symbols or punctuations are used in keywords and identifiers. The only underscore can be used in an identifier.
Example: int, char, while, do.	Example: Geeks_for_Geeks, GFG, Gfg1.

Difference between Keyword and Identifier in C

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