What is the benefit of using #define to declare a constant? ?

Question

What is the benefit of using #define to declare a constant?

Answer 1

You code might run faster, depending on the compiler.

#DEFINE makes a CONSTANT.  As opposed to a variable, like "B=5".

Suppose you write code that says

#define COUNT 5

Let B1 = 3

Let C1 = B1

Let D1 = COUNT

your compiler will generate

**Let B1 = 3

lda  3

sta  B1

** Let C1 = B1

lda   B1

sta  C1

** Let D1 = COUNT

lda  5

sta  D1

In this little progrm there are two pre-defined values, B1 and COUNT.  B1 is a variable and COUNT is a CONSTANT.

Look how much code it take to load C1 with the variable B1, compared to how much code it take to load D1 with the constant COUNT.  In this case using a CONSTANT is almost twice as fast!

The limitation is that the progrm canNOT change a CONSTANT -- to do that you have to recompile.  Programs can always change variables, but the resulting code may be slower.

Answer 2

if you mean in C programming, it's because then you can't accidentally modify the value, in comparison to storing it in a variable in math expressions