C++ Keywords and Identifiers

Keywords

A keywords are the reserved words in programming language with a specific features for each keyword. Keywords always starts with the lower case and cannot be a variable name or constant name. These are predefined by the program and their value cannot be changed.

Example: int, float, public, etc.

The following is the list of 30 keywords in C++ that are also available in C programming language.

auto	break	case	char	const
double	else	enum	extern	float
int	long	register	return	short
struct	switch	typedef	union	unsigned
continue	default	do	for	goto
if	signed	sizeof	static	void
volatile	while

The following is the list of 30 keywords in C++ that are not available in C programming language.

asm	dynamic_cast	namespace	reinterpret_cast	bool
explicit	new	static_cast	false	catch
operator	template	friend	private	class
this	inline	public	throw	const_cast
delete	mutable	protected	true	try
typeid	typename	using	virtual	wchar_t

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Identifiers

Identifiers are nothing but the name assigned to the entities such as variables, functions, arrays, or other user-defined data types. Identifiers are the basics need of programming language.

The name assigned to the entities is unique so that it can be identified during the execution of the program. Identifiers cannot be used as Keywords.

Example: int number;, number being an identifier.

Rules for naming identifiers:

• Identifiers are case-sensitive that is uppercase and lowercase letters are distinct.
• The first letter of identifiers must be a letter or underscore. After the first letter, you can use digits.
• White spaces are not allowed.
• A keyword cannot be used as an identifier.

Some valid and invalid identifiers:

//Valid
Number  
result1  
_multiply  
S2C

//Invalid
Number-2   //special character '-' is present.  
3Sum    //started with digit   
int    // int is a keyword      

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