C++ Keywords

Last Updated : 17 Sep, 2025

Keywords are the reserved words that have special meanings. Since their meanings are reserved, we cannot redefine them or use them for a different purpose.

C++

#include <iostream>
using namespace std;

// 'int' is a keyword 
int main() {
    
    // 'int' is a keyword 
    int age = 20;
    
    // 'if' is a keyword
    if (age > 18) { 
        cout << "Adult";
    }
    
    // 'return' is a keyword 
    return 0;       
}

Output

Adult

How to Identify C++ Keywords

Syntax Highlighting: Most modern IDEs (like Visual Studio, CLion, Code::Blocks) highlight keywords in a different color. This makes them stand out from variables or function names.
Compiler Errors: If you mistakenly use a keyword as a variable name, your code won’t compile. Example:

C++

int return = 10;   // Error: 'return' is reserved

Categorization of C++ Keywords

To make them easier to understand, let’s group C++ keywords by context:

Category	Keywords
Data Types	bool, char, char8_t, char16_t, char32_t, int, long, short, signed, unsigned, float, double, void, wchar_t
Control Flow	if, else, switch, case, default, for, while, do, break, continue, goto
Boolean & Null	true, false, nullptr
Memory Management	new, delete, sizeof, alignas, alignof
Classes & Structs	class, struct, union, enum, friend, mutable, this
Access Specifiers	public, private, protected
Functions & Modifiers	inline, explicit, virtual, override, final, constexpr, consteval, constinit, operator, typedef, using, typename
Templates & Generics	template, concept, requires
Exception Handling	try, catch, throw, noexcept
Casting & Type Info	const_cast, dynamic_cast, reinterpret_cast, static_cast, decltype, typeid
Constants & Storage	const, static, static_assert, extern, register, thread_local, volatile
Modules / Export	export, namespace
Coroutines (C++20)	co_await, co_return, co_yield
Operators (alt spellings)	and, and_eq, or, or_eq, not, not_eq, bitand, bitor, compl, xor, xor_eq
Miscellaneous	asm, auto, return, sizeof

Note: The number of keywords C++ has evolved over time as new features were added to the language. For example, C++ 98 had 63 keywords, C++ 11 had 84 keywords, C++.

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: geeksForGeeks, geeks_for_geeks, gfg, gfg12.