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In C, you must declare a variable's type before using it. C is statically typed — the type is fixed at compile time. The basic data types are int (integers), float (decimals), double (precise decimals), and char (single character). Variable names must start with a letter or underscore.

C Data Types & Format Specifiers

int — Whole numbers: int age = 25; — use %d in printf

float — Decimal numbers: float price = 9.99f; — use %f

double — More precise decimals: double pi = 3.14159; — use %lf

char — Single character: char grade = 'A'; — use %c

char[] — String (array of chars): char name[] = "Alice"; — use %s

Format specifiers tell printf what type to print

Variables Example

Example

#include <stdio.h>

int main() {
    // Declaring variables
    int age = 25;
    float height = 5.9f;
    double salary = 50000.50;
    char grade = 'A';
    char name[] = "Alice";

    // Printing with format specifiers
    printf("Name: %s\n", name);
    printf("Age: %d\n", age);
    printf("Height: %.1f feet\n", height);
    printf("Salary: %.2f\n", salary);
    printf("Grade: %c\n", grade);

    return 0;
}

Try It Yourself: Variables

Try It Yourself: VariablesC

C Editor

✓ ValidTab = 2 spaces

#include <stdio.h>

int main() {
    // Create your own variables!
    char my_name[] = "Your Name";
    int my_age = 20;
    float my_gpa = 8.5f;
    char my_grade = 'A';

    printf("=== My Profile ===\n");
    printf("Name: %s\n", my_name);
    printf("Age: %d years\n", my_age);
    printf("GPA: %.1f\n", my_gpa);
    printf("Grade: %c\n", my_grade);

    // Simple arithmetic
    int a = 10, b = 3;
    printf("\n%d + %d = %d\n", a, b, a + b);
    printf("%d * %d = %d\n", a, b, a * b);

    return 0;
}

Output

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Edit the code on the left, then click Run

C|22 lines|508 chars|✓ Valid syntax

UTF-8

Variables & Data Types

Variables in C

C Data Types & Format Specifiers

Variables Example

Try It Yourself: Variables

Quick Quiz