C++ Structures
Structures (also called structs) are a way to group several related variables into one place.
Each variable in the structure is known as a member of the structure.
Unlike an array , a structure can contain many different data types: int , string , bool , etc.
Create a Structure
To create a structure, use the struct keyword and declare each of its members inside curly braces.
After the declaration, specify the name of the structure variable ( myStructure in the example below):
struct { // Structure declaration
int myNum; // Member (int
variable)
string myString; // Member (string variable)
}
myStructure; // Structure variableAccess Structure Members
To access members of a structure, use the dot syntax ( . ):
Example
// Create a structure variable called myStructure
struct {
int myNum;
string myString;
} myStructure;
// Assign values to members of myStructure myStructure.myNum = 1; myStructure.myString = "Hello World!"; // Print members of myStructure cout << myStructure.myNum << "\n"; cout << myStructure.myString << "\n";One Structure in Multiple Variables
You can use a comma ( , ) to use one structure in many variables:
struct {
int myNum;
string myString;
} myStruct1, myStruct2, myStruct3; // Multiple structure variables separated with commasThis example shows how to use a structure in two different variables:
Example
struct {
string brand;
string model;
int year;
} myCar1, myCar2; // We can add variables by separating them with a comma here
// Put data into the first structure myCar1.brand = "BMW"; myCar1.model = "X5"; myCar1.year = 1999; // Put data into the second structure myCar2.brand = "Ford"; myCar2.model = "Mustang"; myCar2.year = 1969; // Print the structure members cout << myCar1.brand << " " << myCar1.model << " " << myCar1.year << "\n"; cout << myCar2.brand << " " << myCar2.model << " " << myCar2.year << "\n";Named Structures
By giving a name to the structure, you can treat it as a data type. This means that you can create variables with this structure anywhere in the program at any time.
To create a named structure, put the name of the structure right after the struct keyword:
struct car { // This structure is now named "car"
string
brand;
string model;
int year;
};To declare a variable that uses the structure, use the name of the structure as the data type of the variable:
car myCar1;Now the structure can be reused anywhere by using car as the data type:
Example
// Declare a structure named "car"
struct car {
string brand;
string model;
int year;
};
int main() {
// Create a car structure and store it in myCar1; car myCar1; myCar1.brand = "BMW"; myCar1.model = "X5"; myCar1.year = 1999; // Create another car structure and store it in myCar2; car myCar2; myCar2.brand = "Ford"; myCar2.model = "Mustang"; myCar2.year = 1969; // Print the structure members cout << myCar1.brand << " " << myCar1.model << " " << myCar1.year << "\n"; cout << myCar2.brand << " " << myCar2.model << " " << myCar2.year << "\n";
return 0;
}Challenge Task
Create a structure to represent a student. It should have the following members:
- name ( string )
- age ( int )
- grade ( char )
Then
- Create one variable of the structure.
- Assign values to its members.
- Print the values to the screen.
Name: Liam
Age: 35
Grade: ASolution
Runnable example
#include <iostream>
#include <string>
using namespace std;
struct student {
string name;
int age;
char grade;
};
int main() {
student s1;
s1.name = "John";
s1.age = 35;
s1.grade = 'A';
cout << "Name: " << s1.name << "\n";
cout << "Age: " << s1.age << "\n";
cout << "Grade: " << s1.grade << "\n";
return 0;
}