1. What is a Data Type?

A data type tells the compiler what kind of data a variable will store —
like a number, decimal value, or character — and also how much memory to reserve for it.

Each variable in C must be declared with a specific data type.

🧩 Example

#include <stdio.h>

int main() {

  // Create variables

  int myNum = 5;             // Integer (whole number)

  float myFloatNum = 5.99;   // Floating point number

  char myLetter = ‘D’;       // Character

  // Print variables

  printf(“%d\n”, myNum);

  printf(“%f\n”, myFloatNum);

  printf(“%c\n”, myLetter);

  return 0;

}

✅ Output:

5

5.990000

D

2. Basic Data Types in C

3. Why Different Data Types?

Each type is used for a different purpose:

Use int → when you want whole numbers (age, marks, count, etc.)

Use float → when you want decimal values (height, price, temperature)

Use double → when you need very accurate decimal values

Use char → when you want a single character or symbol

4. Basic Format Specifiers

Each data type has a specific format specifier used inside printf()
(to tell C how to print the value).

⚠️ Important Note

It’s very important to use the correct format specifier for each data type.
If you mix them (for example, using %d for a float), the program may show wrong results or even crash.

🧩 Quick Example — Using All Data Types

#include <stdio.h>

int main() {

  int age = 21;

  float height = 5.8;

  double salary = 75000.50;

  char grade = ‘A’;

  printf(“Age: %d\n”, age);

  printf(“Height: %f\n”, height);

  printf(“Salary: %lf\n”, salary);

  printf(“Grade: %c”, grade);

  return 0;

}

✅ Output:

Age: 21

Height: 5.800000

Salary: 75000.500000

Grade: A

🧩 Quick Summary Table