Stupid Question maybe?

[Joe <jbfixurpc () gmail com>]

Apologizes in advance for a simple question. I am finding conflicting
definitions of Class networks. I was always under the impression that a
class "A" network was a /8 a class "B" network was a /16 and a class "C"
network was a /24. Recently, I was made aware that a class "A" was indeed a
/8 and a class "B" was actually a /12 (172.16/172.31.255.255) while a class
"C" is actually a /16.

Is this different depending on the IP segment, i.e. if it is part of a
RC1918 group it is classed differently (maybe a course I missed?) Or aren't
all IP's classed the same.
I was always under the impression, /8 = A, /16 = B, /24=C, so rightly, or
wrongly I've always seen 10.x.x.x as "A", and 192.168.x.x as "B", with
172.16/12 as one that just a VLSM between the two.

Again, apologizes for the simple question, just can't seem to find a solid
answer.

Happy holidays all the same!
-Joe