Structures in C

In C, a structure is a composite data type that groups variables of different data types under a single name. It allows you to create custom data types that can store multiple variables of different data types as members within a single memory block. A structure is defined using the struct keyword followed by the structure name, and its members are listed within curly braces {}.

A structure can be represented as follows:

A structure can be implemented in C as follows:

struct Person {
    char name[50];
    int age;
    float height;
};

In the example above, a structure named Person is defined with three members: name, age, and height. The name member is an array of characters with a maximum size of 50, representing the name of the person. The age member is an integer representing the age of the person, and the height member is a floating-point number representing the height of the person.

Operations supported by Structures

1. Declaration: Structures are declared using a structure definition, which specifies the data members and their types. For example:

struct Point {
    int x;
    int y;
};

2. Initialization: Structures can be initialized when they are declared or after they are declared. For example:

struct Point p1 = {0, 0}; // Initializing at declaration
struct Point p2; // Declaration
p2.x = 1; // Initialization after declaration
p2.y = 2;

3. Accessing data members: You can access the data members of a structure using the dot (.) operator. For example:

struct Point p1 = {3, 4};
int x = p1.x; // Accessing the x data member
int y = p1.y; // Accessing the y data member

4. Modifying data members: You can modify the data members of a structure using the dot (.) operator. For example:

struct Point p1 = {3, 4};
p1.x = 5; // Modifying the x data member
p1.y = 6; // Modifying the y data member

5. Comparison: You can compare structures for equality or inequality using the equality (==) and inequality (!=) operators, respectively. For example:

struct Point p2 = {3, 4};
if (p1.x == p2.x && p1.y == p2.y) {
    // p1 and p2 are equal
}

6. Passing structures to functions: You can pass structures as arguments to functions, either by value or by reference. By value means a copy of the structure is passed, and by reference means a pointer to the structure is passed. For example:

void printPoint(struct Point p) {
    printf("x: %d, y: %d\n", p.x, p.y);
}

struct Point p1 = {3, 4};
printPoint(p1); // Passing by value

void modifyPoint(struct Point* p) {
    p->x = 5;
    p->y = 6;
}

struct Point p2 = {3, 4};
modifyPoint(&p2); // Passing by reference

7. Array of structures: You can create arrays of structures to store multiple instances of the same type of data. For example:

struct Point points[3]; // Array of 3 Point structures

points[0].x = 1;
points[0].y = 2;
points[1].x = 3;
points[1].y = 4;
points[2].x = 5;
points[2].y = 6;

Structures can also be defined within structures to create nested or hierarchical data structures. Structures are commonly used in C for organizing and storing data in a structured manner, such as representing complex objects, data records, or configurations.

The program in this repository demonstrates the implementation of a structure in C.

Code:

// A. creating a database of vehicles by storing information like:
// 1. name
// 2. manufacturing year
// 3. cost
// 4. category (high end (H) / middle (M) / low end (L))
// make a structure to store the above information about a vehicle.



#include <stdio.h>

// creating a structure and naming it 'car'
struct car
{
	char name[50];
	int mYear;
	int cost;
	char category;
};

struct car model[3];

int main()
{
	// int i, j;
	
	// declaring an array of the struct data type 'car' and calling it 'model'
	
	// taking user input for the name, manufacturing year, cost and category
	//printf("Name: ");
	//scanf("%s", &model.name);
	
	//printf("Manufacturing Year: ");
	//scanf("%d", &model.mYear);
	
	//printf("Cost: ");
	//scanf("%d", &model.cost);
	
	//printf("%s %d %d", model.name, model.mYear, model.cost);
	
	
	/*
	// storing details of 10 (3 for now) cars in an array
	for(i = 0; i < 3; i++)
	{
		printf("Name: ");
		scanf("%s", &model[i].name);
	
		printf("Manufacturing Year: ");
		scanf("%d", &model[i].mYear);
		
		printf("Cost: ");
		scanf("%d", &model[i].cost);		
		
		printf("\n\n\n");
	}
	
	
	printf("Available Database: \n\n");
	printf("Name  MYear  Cost \n");
	
	for(j = 0; j < 3; j++)
	{
		printf("%s  %d  %d \n", model[j].name, model[j].mYear, model[j].cost);
	}
	*/
	
	userInput();
	printInput();
	
	return 0;
}



// B. make two functions: one takes user input, the other prints it

void userInput()
{
	int i;
	
	// storing details of 10 (3 for now) cars in an array
	for(i = 0; i < 3; i++)
	{
		printf("Name: ");
		scanf("%s", &model[i].name);
	
		printf("Manufacturing Year: ");
		scanf("%d", &model[i].mYear);
		
		printf("Cost: ");
		scanf("%d", &model[i].cost);		
		
		printf("\n\n\n");
	}
		
}

void printInput()
{
	int j;
	
	printf("Available Database: \n\n");
	printf("Name  MYear  Cost \n");
	
	for(j = 0; j < 3; j++)
	{
		printf("%s  %d  %d \n", model[j].name, model[j].mYear, model[j].cost);
	}
	
}

Output: