(K&R) At least the first 31 characters of an internal name are significant?

Question

When taken literally, it makes sense, but what exactly does it mean to be a significant character of a variable name?

I\'m a beginning learner of C using K&R. He

Answer 1

It just means that if you have two variables named

abcdefghijklmnopqrstuvwxyz78901A,

and

abcdefghijklmnopqrstuvwxyz78901B,

that there is no guarantee that will be treated as different, separate variables...