C Structures Tutorial | How to Define & Use Structs in C

A **Struct** is a collection of variables (called "members" or "fields") that can be of different data types. Structures are used to represent real-world entities like a Student, a Product, or a Point in a 2D plane.

1. Defining and Declaring a Struct

To use a structure, you must first define its template using the struct keyword. This tells the compiler what the "package" looks like.

// Defining a structure template
struct Student {
    int id;
    char name[50];
    float gpa;
};

int main() {
    // Declaring a variable of type 'struct Student'
    struct Student s1;
    return 0;
}

2. Accessing Struct Members

To access or assign values to the members of a structure, we use the **Dot Operator** (.).

struct Student s1;

s1.id = 101;
s1.gpa = 3.8;
strcpy(s1.name, "Alice"); // Use strcpy for strings!

printf("Student Name: %s", s1.name);

3. Initializing Structs

You can initialize a struct in a single line, similar to an array, by placing values in curly braces in the same order they were defined.

4. Copying Structures

One of the best features of structs is that you can copy all the data from one struct to another using a simple assignment operator (=), which isn't possible with arrays.

5. Nested Structures

A structure can also contain another structure as one of its members. This is useful for complex data, like a Person having an Address.

struct Address {
    char city[20];
    int pin;
};

struct Person {
    char name[20];
    struct Address addr; // Nested struct
};

6. Comparison: Structs vs. Arrays

Feature	Array	Structure
Data Types	Homogeneous (All same)	Heterogeneous (Different)
Access Method	Index number [0]	Member name (.id)
Assignment	Cannot use `=` for full array	Can use `=` to copy all data

Feature

Array

Structure

Data Types

Homogeneous (All same)

Heterogeneous (Different)

Access Method

Index number [0]

Member name (.id)

Assignment

Cannot use = for full array

Can use = to copy all data