Question: 'machine' epsilon

Working in usual programming languages there is a largest machine epsilon
with 1 + epsilon != 1.

Now I am working with floats in Maple and want something similar: given a
real constant x (as positive floating point number) and m:=floor(log10(x))
(= ilog10(x) scales the x (down or up) to be of size 1). 

My question is:

Does the following always evaluate to "true"

  x + epsilon = x; evalf(eval(%, epsilon= 1/10^(Digits-m)));

and to "false" if taking m+1 instead?

Sorry, stupidly can not find the answer in the docu ...
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