Variables and Data Types in C

What is a Variable?

A variable is a name given to a memory location that stores a value. This value can change during the execution of a program.

Syntax:

datatype variableName = value;

Example:

int age = 20;
float height = 5.8;
char grade = 'A';

Rules for Naming Variables

Must begin with a letter or underscore (_)
Can contain letters, digits, and underscores
No special characters or spaces
Case sensitive (Age and age are different)

What are Data Types?

Data types tell the compiler what kind of data a variable can hold. C has several types:

1. int (Integer)

Stores whole numbers without decimals.

int num = 25;

2. float (Floating Point)

Stores decimal numbers (single precision).

float temp = 36.6;

3. double (Double Precision)

Stores larger decimal numbers with more precision than float.

double distance = 1234.56789;

4. char (Character)

Stores a single character enclosed in single quotes.

char letter = 'B';

5. void (Empty Type)

Represents no value. Commonly used in functions to indicate no return value.

void printHello() {
  printf("Hello");
}

6. short and long (Integer Variants)

Used to store smaller or larger integers.

short a = 100;
long b = 1000000;

Complete Example

#include <stdio.h>

int main() {
    int age = 20;
    float marks = 87.5;
    char grade = 'A';

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

    return 0;
}