c - #Define VS Variable

Question

I cannot understand what is the difference between:

#define WIDTH 10 

and

int width = 10;

What are the benefits of using the first or the second?

Answer 1

Well, there is a great difference. You can change the value of width, you can take its address, you can ask for its size and so on. With WIDTH, it will be just replaced with a constant 10 everywhere, so the expression ++WIDTH doesn't make any sense. Ono the other side, you can declare an array with WIDTH items, whereas you cannot declare an array with width items.

Summing it up: the value of WIDTH is known at compile time and cannot be changed. The compiler doesn't allocate memory for WIDTH. On the contrary, width is a variable with initial value 10, its further values are not known at compile time; the variable gets its memory from the compiler.