Constants vs. Variables in C: Key Differences Explained
In C, a const is a named value that can never change after it is set, while a variable is a named box whose contents can be altered at any time.
People confuse them because both occupy memory and look similar in code. The real mix-up happens when devs forget const is a promise to the compiler and future teammates, not just a decoration.
Key Differences
const locks the value at compile time; variables remain open for reassignment. Using const lets the compiler fold constants, save RAM, and catch accidental writes.
Which One Should You Choose?
Choose const for magic numbers, buffer sizes, or lookup tables. Pick variables for counters, user input, or anything that must evolve while the program runs.
Examples and Daily Life
const float PI = 3.14159; prevents bugs in your circle math, while int score = 0; can climb as the player racks up points.
Can a const ever change?
Only via pointer tricks or casts—doing so is undefined behavior and breaks the promise.
Is const stored in ROM?
Not always; it may sit in RAM marked read-only or get folded into machine code.
When should I avoid const?
Avoid it when the value must come from runtime input, sensors, or files.