Structures

Structures

A structure in C++ stores together data elements under a single name. The data elements, also called data memebers, can be of different data types.

Syntax

A structure is defined with:

  1. The struct keyword in the beginning.
  2. Curly brackets { } to define the body.
  3. A semicolon ; at the end.
struct name {
  member1_type member1_name;
  member2_type member2_name;
  member3_type member3_name;
};

Example

The example below is a struct with the name coder:

struct coder {
long id;
char name[30];
char username[15];
};

This structure contains three members:

  • id
  • name
  • username

Declaring and Initializing Structure Variables

The members of a structure can be initialized inside the structure definition in C++11 and higher.

An example of declaring and initializing a structure variable:

#include <iostream>
struct coordinates {
int x;
int y;
};
int main() {
// Declaring variable c1
struct coordinates c1;
c1.x = 2;
c1.y = 2;
// Declaring and initializing variable c2
struct coordinates c2 = { 0, 1 };
std::cout << "x1 = " << c1.x << ", y1 = " << c1.y << "\n"; // For variable c1
std::cout << "x2 = " << c2.x << ", y2 = " << c2.y << "\n"; // For variable c2
return 0;
}

The output will look like this:

x1 = 2, y1 = 2
x2 = 0, y2 = 1

Array of Structure

Like other primitive data types, we can create an array of structures.

An example of array of structure:

#include <iostream>
struct coordinates {
int x;
int y;
};
int main() {
struct coordinates c[4];
int i;
for (i = 0; i < 4; i++)
std::cin >> c[i].x >> c[i].y;
for (i = 0; i < 4; i++) {
std::cout << "x" << i+1 << "=" << c[i].x << "\t";
std::cout << "y" << i+1 << "=" << c[i].y << "\n";
}
return 0;
}

Input:

1 0
1 2
1 1
0 2

Output:

x1 = 1 y1 = 0
x2 = 1 y2 = 2
x3 = 1 y3 = 1
x4 = 0 y4 = 2

Nested Structure

A structure’s variable can also be a member of, or nested in, another structure.

In the example below, a DOB structure is nested in a coder structure:

struct coder {
long id;
char name[30];
char username[15];
struct DOB {
int month;
int day;
int year;
} d;
} bjarne;

The d is the structure’s variable for struct DOB and bjarne is the structure variable for struct coder.

Members of a nested structure can be accessed using var1.var2.member1.

Initializing a member of the structure DOB from the example above:

bjarne.d.day = 10;
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