C Tutorial

VARIABLES IN C

Variables in C

A variable in C is a name given to a memory location that stores data. It acts like a container for data that your program can manipulate. Each variable must be declared with a specific data type.

📘 Remember: Variables must be declared before they are used.

📌 Variable Declaration Syntax

data_type variable_name;

Or declare and initialize in one line:

data_type variable_name = value;

🧪 Example

#include <stdio.h>

int main() {
    int age = 20;
    float height = 5.9;
    char grade = 'A';

    printf("Age: %d\\n", age);
    printf("Height: %.1f\\n", height);
    printf("Grade: %c", grade);

    return 0;
}

🧱 Variable Types

int - for integers (e.g., 5, -3)
float - for decimal numbers (e.g., 3.14)
char - for single characters (e.g., 'A')
double - for large/precise decimal numbers

✅ Rules for Naming Variables

Must start with a letter (A–Z or a–z) or underscore (_)
Can contain letters, digits (0–9), and underscores
No special symbols like @, $, etc.
Cannot use reserved C keywords (e.g., int, return)

💡 Tip: Use meaningful names. For example, use marks instead of m to make code more readable.

❌ Common Mistakes

🚫 Using undeclared variables
🚫 Misspelling variable names
🚫 Using wrong format specifiers in printf (e.g., using %d for a float)

📝 Try It Yourself

Declare 3 variables: name (char), marks (float), roll_no (int)
Assign values and print them using printf

🧠 Variable Tip: You can declare multiple variables of the same type in one line:
int a = 5, b = 10, c = 15;

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