struct (C++)
The latest version of this topic can be found at struct (C++).
The struct keyword defines a structure type and/or a variable of a structure type.
Syntax
[template-spec] struct[ms-decl-spec] [tag [: base-list ]]
{
member-list
} [declarators];
[struct] tag declarators;
Parameters
template-spec
Optional template specifications. For more information, refer to Template Specifications.
struct
The struct keyword.
ms-decl-spec
Optional storage-class specification. For more information, refer to the __declspec keyword.
tag
The type name given to the structure. The tag becomes a reserved word within the scope of the structure. The tag is optional. If omitted, an anonymous structure is defined. For more information, see Anonymous Class Types.
base-list
Optional list of classes or structures this structure will derive its members from. See Base Classes for more information. Each base class or structure name can be preceded by an access specifier (public, private, protected) and the virtual keyword. See the member-access table in Controlling Access to Class Members for more information.
member-list
List of structure members. Refer to Class Member Overview for more information. The only difference here is that struct is used in place of class.
declarators
Declarator list specifying the names of the class. Declarator lists declare one or more instances of the structure type. Declarators may include initializer lists if all data members of the class are public. Initializer lists are common in structures because data members are public by default. See Overview of Declarators for more information.
Remarks
A structure type is a user-defined composite type. It is composed of fields or members that can have different types.
In C++, a structure is the same as a class except that its members are public by default.
For information on managed classes and structs, see Classes and Structs.
Using a Structure
In C, you must explicitly use the struct keyword to declare a structure. In C++, you do not need to use the struct keyword after the type has been defined.
You have the option of declaring variables when the structure type is defined by placing one or more comma-separated variable names between the closing brace and the semicolon.
Structure variables can be initialized. The initialization for each variable must be enclosed in braces.
For related information, see class, union, and enum.
Example
#include <iostream>
using namespace std;
struct PERSON { // Declare PERSON struct type
int age; // Declare member types
long ss;
float weight;
char name[25];
} family_member; // Define object of type PERSON
struct CELL { // Declare CELL bit field
unsigned short character : 8; // 00000000 ????????
unsigned short foreground : 3; // 00000??? 00000000
unsigned short intensity : 1; // 0000?000 00000000
unsigned short background : 3; // 0???0000 00000000
unsigned short blink : 1; // ?0000000 00000000
} screen[25][80]; // Array of bit fields
int main() {
struct PERSON sister; // C style structure declaration
PERSON brother; // C++ style structure declaration
sister.age = 13; // assign values to members
brother.age = 7;
cout << "sister.age = " << sister.age << '\n';
cout << "brother.age = " << brother.age << '\n';
CELL my_cell;
my_cell.character = 1;
cout << "my_cell.character = " << my_cell.character;
}
// Output:
// sister.age = 13
// brother.age = 7
// my_cell.character = 1