[Yum] Difference between YUM and APT

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Hello,

Here is my first posting and a question.

I read a page "Obvious Questions" through:
Q. Why not just use apt-rpm?
A. a number of reasons

But, I do not understand well still now.
A number of "GOOD" reasons are raised for using YUM,
instead of APT. It seems to me that any useful tool
has always have two sides: merits and demerits.
So that, it  would be appreciated if any explanations
are given to these two package managers.

Or, there is no demerits at all to introduce YUM, compared
with APT? That is a point, because Fedora Core Release 1
(Yarrow) offers both YUM and APT, adding up2date, which
may confuse users.

Thank you.

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