C++語言繼承了C語言的struct，并且加以擴充。在C語言中struct是只能定義數據成員，而不能定義成員函數的。而在C++中，struct類似于class，在其中既可以定義數據成員，又可以定義成員函數。

結構類型是用戶定義的復合類型，它可由不同類型的字段或成員構成。在C++中，struct與class基本是通用的，唯一不同的是如果使用class關鍵字，類中定義的成員變量或成員函數默認都是private屬性的，而采用struct關鍵字，結構體中定義的成員變量或成員函數默認都是public屬性的。

???????? 在C中，必須顯示使用struct關鍵字來聲明結構。在C++中，不需要在定義該類型之后使用struct關鍵字。可以選擇在定義結構類型時，通過在右大括號和分號之間放置一個或多個逗號分隔的變量名稱來聲明變量。可以初始化結構變量，每個變量的初始化必須括在大括號中。

???????? Differences between C struct & C++ struct:

(1)、 C structure can't contain functions means only data members are allowed, but structure in C++ can have both functions &? data members.

(2)、 struct keyword is necessary in C to create structure type variable, but it is? redundant & not necessary in C++.

(3)、 Size of empty structure is undefined behavior in C, but it is always 1 in C++.

(4)、 Structure in C can't have static members, but C++ structure can have static members.

(5)、 Structure members can't be directly initialized inside the struct in C, but it is allowed in C++ since C++11.

(6)、 We can have both pointers and references to struct in C++, but only pointers to structs are allowed. (References aren't feature of C language).

(7)、 C++ also have .* and -> operators to access individual members of struct, but C doesn't have such kind of operators.

(8)、 struct declaration establishes a? scope in C++ and not in C, which makes member enumerators and nested structs possible in C++(you can *write* them inside a struct in C, but they escape and become local to whatever function the parent struct is in).

(9)、 In C, we need to use struct tag whenever we declare a struct variable. In C++, the struct tag is not necessary.

(10)、C++ structures are very similar to a class, with the only difference being that in a class, all members are private by default. But in a C++ structure, all members are public by default. In C, there is no concept of public or private.

(11)、C++ structures can have member functions, whereas C structures cannot.

(12)、You can have constructors, destructors, copy constructors and so on in C++ structures. You cannot in C structures.

(13)、C++ structures can have static members, whereas C structures cannot.

下面是從其他文章中copy的測試代碼，詳細內容介紹可以參考對應的reference：

#include "struct.hpp"
#include <cstring>
#include <cstdlib>
#include <iostream>///
// reference: https://msdn.microsoft.com/zh-cn/library/64973255.aspx
struct PERSON {   // Declare PERSON struct typeint age;   // Declare member typeslong ss;float weight;char name[25];
} family_member;   // Define object of type PERSONstruct CELL {   // Declare CELL bit fieldunsigned short character : 8;  // 00000000 ????????unsigned short foreground : 3;  // 00000??? 00000000unsigned short intensity : 1;  // 0000?000 00000000unsigned short background : 3;  // 0???0000 00000000unsigned short blink : 1;  // ?0000000 00000000
} screen[25][80];       // Array of bit fields int test_struct1()
{struct PERSON sister;   // C style structure declarationPERSON brother;   // C++ style structure declarationsister.age = 13;   // assign values to membersbrother.age = 7;std::cout << "sister.age = " << sister.age << '\n';std::cout << "brother.age = " << brother.age << '\n';CELL my_cell;my_cell.character = 1;std::cout << "my_cell.character = " << my_cell.character<<'\n';return 0;
}//
// reference: http://www.tutorialspoint.com/cplusplus/cpp_data_structures.htm
struct Books {char  title[50];char  author[50];char  subject[100];int   book_id;
};void printBook(struct Books book)
{std::cout << "Book title : " << book.title << std::endl;std::cout << "Book author : " << book.author << std::endl;std::cout << "Book subject : " << book.subject << std::endl;std::cout << "Book id : " << book.book_id << std::endl;
}int test_struct2()
{struct Books Book1;        // Declare Book1 of type Bookstruct Books Book2;        // Declare Book2 of type Book// book 1 specificationstrcpy(Book1.title, "Learn C++ Programming");strcpy(Book1.author, "Chand Miyan");strcpy(Book1.subject, "C++ Programming");Book1.book_id = 6495407;// book 2 specificationstrcpy(Book2.title, "Telecom Billing");strcpy(Book2.author, "Yakit Singha");strcpy(Book2.subject, "Telecom");Book2.book_id = 6495700;// Print Book1 infoprintBook(Book1);// Print Book2 infoprintBook(Book2);return 0;
}///
// reference: http://www.dummies.com/how-to/content/how-to-build-a-structure-template-in-c.html
template<typename T>
struct Volume {T height;T width;T length;Volume(){height = 0;width = 0;length = 0;}T getvolume(){return height * width * length;}T getvolume(T H, T W, T L){height = H;width = W;length = L;return height * width * length;}
};int test_struct3()
{Volume<int> first;std::cout << "First volume: " << first.getvolume() << std::endl;first.height = 2;first.width = 3;first.length = 4;std::cout << "First volume: " << first.getvolume() << std::endl;Volume<double> second;std::cout << "Second volume: " << second.getvolume(2.1, 3.2, 4.3) << std::endl;std::cout << "Height: " << second.height << std::endl;std::cout << "Width: " << second.width << std::endl;std::cout << "Length: " << second.length << std::endl;return 0;
}///
// reference: http://www.java2s.com/Code/Cpp/Class/Constructoranddestructorinsideastruct.htm
struct StringClass
{StringClass(char *ptr);~StringClass();void show();
private:char *p;int len;
};StringClass::StringClass(char *ptr)
{len = strlen(ptr);p = (char *)malloc(len + 1);if (!p) {std::cout << "Allocation error\n";exit(1);}strcpy(p, ptr);
}StringClass::~StringClass()
{std::cout << "Freeing p\n";free(p);
}void StringClass::show()
{std::cout << p << " - length: " << len;std::cout << std::endl;
}int test_struct4()
{StringClass stringObject1("www.java2s_1.com."), stringObject2("www.java2s_2.com.");stringObject1.show();stringObject2.show();return 0;
}