(It may be that this question "does not show research effort". Sorry -- it's not a question with mathematical content, so it's impossible to figure out the answer; it's a question about who said what when, and I have no idea where to look for the answer...)
Recent comments about one of our regulars being a better mathematician than Cauchy reminded me::
I gather that Cauchy never referred to "cauchy sequences"; rather his definition of "convergent sequence of reals" was the same as our definition of "cauchy sequence of reals".
Q1: Is that more or less correct?
If yes: Presumably he used the fact which is expressed in modern terminology by saying that every cauchy sequence of reals is convergent.
Q2: Was he aware that this fact amounts to a significant assumption about $\Bbb R$, or did he regard the fact as a self-evident truth? (Come to think of it there's a third possibility; that he proved (or "proved") the fact. This seems unlikely, but if so he proved it from what assumptions?)