Why use #define instead of a variable

Question

What is the point of #define in C++? I\'ve only seen examples where it\'s used in place of a \"magic number\" but I don\'t see the point in just giving that val

Answer 1

I got in trouble at work one time. I was accused of using "magic numbers" in array declarations.

Like this:

int Marylyn[256], Ann[1024];

The company policy was to avoid these magic numbers because, it was explained to me, that these numbers were not portable; that they impeded easy maintenance. I argued that when I am reading the code, I want to know exactly how big the array is. I lost the argument and so, on a Friday afternoon I replaced the offending "magic numbers" with #defines, like this:

 #define TWO_FIFTY_SIX 256
 #define TEN_TWENTY_FOUR 1024

 int Marylyn[TWO_FIFTY_SIX], Ann[TEN_TWENTY_FOUR];

On the following Monday afternoon I was called in and accused of having passive defiant tendencies.