C Tutorial

CONSTANTS IN C

Constants in C

Constants in C are fixed values that do not change during the execution of a program. Once defined, a constant cannot be altered.

🔐 Why Use Constants? They improve code readability, prevent accidental changes, and make maintenance easier.

✏️ Declaring Constants

Using const keyword: Declares a variable as constant.
Using #define preprocessor: Defines a constant value globally.

🧪 Example

#include <stdio.h>

#define PI 3.14  // Constant using #define

int main() {
    const int MAX = 100;  // Constant using const keyword

    printf("PI is: %f\\n", PI);
    printf("Max limit is: %d\\n", MAX);

    return 0;
}

✅ Key Points

const is type-safe and preferred for variables.
#define is a preprocessor directive and has no type.
You can't change the value of a constant after its definition.

💡 Tip: Use meaningful names for constants, e.g., MAX_SPEED, PI, etc.

❌ Common Mistakes

🚫 Trying to change the value of a constant after declaring it.
🚫 Forgetting semicolon after const declaration.

📝 Try It Yourself

Declare a constant using const to store the maximum marks in a test.
Define a constant using #define for the value of gravity (e.g., 9.8).

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