Defining Struture in C

Declaring a Structure

struct structure_name;

• This is just a declaration of the structure type, which tells the compiler that a structure with that name exists. It doesn't actually allocate any memory for the structure.

Defining a Structure

struct structure_name {
   data_type member1;
   data_type member2;
   ...
   data_type memberN;
};

• This defines the structure type by specifying the name of the structure and its member variables, each of which has its own data type.

For example:

Let's define a simple structure for a point in two-dimensional space, with an x and y coordinate:

struct point {
   int x;
   int y;
};

• This code defines a structure type called point, which has two member variables of type int called x and y.

• Once you have declared and defined a structure type, you can create variables of that type, as shown in the following example. This code creates a variable called p of type point.

struct point p;

• You can also initialize the member variables of a structure variable at the time of declaration, like this:

struct point p = {10, 20};

This code creates a variable called p of type point and initializes its x and y member variables to 10 and 20, respectively.

Example

This program shows how to declare, define, and create an instance of a structure:

#include <stdio.h>

// Declare the structure type
struct point
{
    int x;
    int y;
};

int main()
{
    // Define a variable of the structure type
    struct point p;

    // Assign values to the structure members
    p.x = 10;
    p.y = 20;

    // Print out the values of the structure members
    printf("x = %d, y = %d\n", p.x, p.y);

    return 0;
}

Output:

Explanation

• We first declare the point structure type, which has two member variables of type int called x and y.
• We then define a variable of the structure type called p in the main() function.
• We assign values to the x and y members of the p structure variable using the dot (.) operator to access the members.
• Finally, we print out the values of the x and y members using printf().

Output:

x = 10, y = 20