**Course Title:** Mastering C: From Fundamentals to Advanced Programming **Section Title:** Structures and Unions **Topic:** Defining and using structures in C. ### Introduction to Structures in C In C programming, a structure is a collection of variables of different data types that can be stored together in memory. Structures allow us to organize related data into a single unit, making it easier to access and manipulate the data. ### Defining Structures A structure is defined using the `struct` keyword followed by the name of the structure and a pair of curly brackets `{}` that contain the member variables. Here is an example: ```c struct Person { int age; char name[50]; float height; }; ``` This defines a structure named `Person` with three member variables: `age`, `name`, and `height`. ### Declaring Structure Variables To use a structure, we need to declare variables of that structure type. We can declare structure variables in two ways: 1. **Method 1:** ```c struct Person person1; ``` This declares a variable `person1` of type `Person`. 2. **Method 2:** We can also declare multiple structure variables when we define the structure: ```c struct Person { int age; char name[50]; float height; } person1, person2; ``` This declares two variables `person1` and `person2` of type `Person`. ### Accessing Structure Members To access the members of a structure, we use the dot (`.`) operator. Here is an example: ```c int main() { struct Person person1; person1.age = 25; strcpy(person1.name, "John"); person1.height = 175.5; printf("Age: %d\n", person1.age); printf("Name: %s\n", person1.name); printf("Height: %.2f\n", person1.height); return 0; } ``` This code accesses the `age`, `name`, and `height` members of the `person1` structure and assigns them values. It then prints out these values. ### Initializing Structure Variables Structure variables can be initialized when they are declared. We can initialize structure variables in two ways: 1. **Method 1:** ```c struct Person person1 = {25, "John", 175.5}; ``` This initializes the `person1` structure variable with the specified values. 2. **Method 2:** ```c struct Person person1 = {.age = 25, .height = 175.5}; ``` This initializes the `age` and `height` members of the `person1` structure variable with the specified values. The `name` member will be initialized with an empty string. ### Structure Arrays We can also declare arrays of structures. Here is an example: ```c struct Person persons[5]; ``` This declares an array `persons` that can hold five `Person` structures. ### Structure Pointers We can also declare pointers to structures. Here is an example: ```c struct Person *personPtr; ``` This declares a pointer `personPtr` that can point to a `Person` structure. Please refer to our resource for more details on structure and structure Pointers: [For Structure Basics -](https://www.tutorialspoint.com/cprogramming/c_structures) [For Pointers and Structure -](https://www.gnu.org/software/gnu-c-manual/gnu-c-manual.html#Pointers-and-Structures) **Example Use Case:** Here is an example program that uses structures to store information about students: ```c #include <stdio.h> #include <string.h> struct Student { int rollNumber; char name[50]; float marks; }; int main() { struct Student students[5]; for (int i = 0; i < 5; i++) { printf("Enter roll number of student %d: ", i + 1); scanf("%d", &students[i].rollNumber); printf("Enter name of student %d: ", i + 1); scanf("%s", students[i].name); printf("Enter marks of student %d: ", i + 1); scanf("%f", &students[i].marks); } printf("Students' Information:\n"); for (int i = 0; i < 5; i++) { printf("Roll Number: %d\n", students[i].rollNumber); printf("Name: %s\n", students[i].name); printf("Marks: %.2f\n\n", students[i].marks); } return 0; } ``` This program stores information about five students in an array of structures and then prints out the information. **Do you have any questions or need further clarification on this topic? Please leave a comment below, and we will be happy to help.** In the next topic, we will be discussing 'Nested structures and arrays of structures.'