Definition of structure in c plus plus?

Answer 1

A structure is a collection of variables referenced under one name, providing a convenient means of keeping related information together. A structure declaration forms a template that may be used to create structure objects (that is, instances of a structure). The variables that make up the structure are called members. (Structure members are also commonly referred to as elements or fields).

Answer 2

A structure (defined with the C++ keyword struct) is a data type definition, no different to a data type defined with the class keyword. Either can be used to define a class. The only difference between the two is that class members are private by default while struct members are public by default. By the same token, derivatives of a struct employ public inheritance by default while derivatives of a class employ private inheritance by default.

As a result, the following two data types are exactly equivalent:

struct X { int m_data; }

class Y { public: int m_data; }

Similarly, the following are exactly equivalent:

struct X { private: int m_data; }

class Y { int m_data; }

Because structs default to public access and inheritance, the struct keyword is typically used to define PODs (plain old datatypes) which are functionally the same as a C-style struct and thus provide backward compatibility with C code. You can also use the class keyword (with public access) to define a POD, however for consistency it is best to use a class when defining a C++ data type and a struct when defining a POD or C data type. All structures defined in C are inherently POD-like (there is no class data type in C).