(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 means that :

foobar1
foobar2

might be the same external name, because only the first 6 characters need be considered. The single case means that upper and lower case names need not be distinguished.

Please note that almost all modern linkers will consider much longer names, thogh there will still be a limit, dependent on the linker.