Unit 9 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 variable

Access Structure Members

To access members of a structure, use the dot syntax (.):

Example

Assign data to members of a structure and print it:

// 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 commas

This example shows how to use a structure in two different variables:

Example

Use one structure to represent two cars:

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 myDataType { // This structure is named "myDataType"

int myNum;

string myString;

};

To declare a variable that uses the structure, use the name of the structure as the data type of the variable:

myDataType myVar;

Example

Use one structure to represent two cars:

// 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;

}