C Academy · Lesson

const Variables

Make values read-only.

What const Means

The const keyword tells the compiler a variable's value must not change after initialization.

If you try to modify it later, compilation fails. This protects values that should stay fixed.

const int MAX_USERS = 100;

You must give a const variable its value when you declare it, because you cannot assign to it afterward.

Here PI is initialized once and used like any normal variable for reading.

#include <stdio.h>
int main(void) {
    const double PI = 3.14159;
    printf("%f\n", PI);
    return 0;
}