C++ keyword: class

 

C++

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C++ language

General topics
Preprocessor Comments	Keywords Escape sequences
Flow control
Conditional execution statements
if	switch
Iteration statements (loops)
for range-for (C++11)	while do-while
Jump statements
continue - break	goto - return
Functions
Function declaration
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inline specifier
Dynamic exception specifications (until C++17*)
noexcept specifier (C++11)
Exceptions
throw-expression try block	handler
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Types
Fundamental types Enumeration types Function types	Class/struct types Union types
Specifiers
const/volatile decltype (C++11) auto (C++11)	constexpr (C++11) consteval (C++20) constinit (C++20)
Storage duration specifiers
Initialization
Default-initialization Value-initialization Zero-initialization Copy-initialization Direct-initialization	Aggregate initialization List-initialization (C++11)   Constant initialization Reference initialization

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Value categories Order of evaluation	Operators Operator precedence
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Boolean - Integer - Floating-point
Character - String - nullptr (C++11)
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Implicit conversions static_cast const_cast	Explicit conversions dynamic_cast reinterpret_cast
Memory allocation
new expression	delete expression
Classes
Class declaration Constructors this pointer	Access specifiers friend specifier
Class-specific function properties
Virtual function override specifier (C++11)   final specifier (C++11)	explicit (C++11) static
Special member functions
Default constructor Copy constructor Move constructor (C++11)	Copy assignment Move assignment (C++11) Destructor
Templates
Class template Function template	Template specialization Parameter packs (C++11)
Miscellaneous
Inline assembly	History of C++

 

Keywords

alignas (C++11) alignof (C++11) and and_eq asm auto (*) bitand bitor bool break case catch char char8_t (C++20) char16_t (C++11) char32_t (C++11) class compl concept (C++20) const consteval (C++20)     constexpr (C++11) constinit (C++20) const_cast continue co_await (C++20) co_return (C++20) co_yield (C++20) decltype (C++11) default delete	do double dynamic_cast else enum explicit export extern false float for friend goto if inline int long mutable namespace new noexcept (C++11)     not not_eq nullptr (C++11) operator or or_eq private protected public register	reinterpret_cast requires (C++20) return short signed sizeof (*) static static_assert (C++11) static_cast struct switch template this thread_local (C++11) throw true try typedef typeid typename union unsigned using virtual void volatile wchar_t while xor xor_eq
Identifiers with special meaning
final (C++11) import (C++20)	module (C++20) override (C++11)

 

Usage

• declaration of a class

declaration of a scoped enumeration type

(since C++11)

• In a template declaration, class can be used to introduce type template parameters and template template parameters
• If a function or a variable exists in scope with the name identical to the name of a class type, class can be prepended to the name for disambiguation, resulting in an elaborated type specifier

Example

Run this code

class Foo; // forward declaration of a class
 
class Bar  // definition of a class
{
public:
    Bar(int i) : m_i(i) {}
private:
    int m_i;
};
 
template<class T> // template argument
void qux()
{
    T t;
}
 
enum class Pub // scoped enum, since C++11
{
    b, d, p, q
};
 
int main()
{
    Bar Bar(1); // variable Bar hides type Bar
    Bar Bar2(2); // compiler error
    class Bar Bar3(3); // elaborated type
}

See also

• struct, union

final

(since C++11)

• enum
• typename
• template

concept, requires

(since C++20)