Q:

Difference Reserved Class B Networks 192.168 vs 172.16

So I understand that there used to be classful addresses allocated depending on the first octet of an IP a long time ago. Of those classes, private IP address ranges were given in each.
Class A 10.*.*.*
Class B 172.16-31.*.*
Class C 192.168.0-255.*

I understand that according the RFC 1918, because 192.168 technically starts in the class C range, it should be considered 256 class C networks. However, because there are 256 available class C networks in 192.168.xxx.xxx, would it be incorrect to refer to this as 1 class B network?

A:

A 'network' or 'subnet' is a set of ip-numbers that can connect to each other without the use of a router. A class C network has a maximum of 256 such ip-addresses. To get from one subnet to another subnet, a router is required. You can not call the 192.168.xxx.yyy block a single class B subnet, because the hosts at 192.168.1.xxx cannot directly connect to hosts in 192.168.2.xxx. The hosts are in different subnets.
192.168.xxx.yyy is an ip-block of 256 private class C networks. Classed networks assume fixed network masks for particular ip-ranges. So, for the networks in block 192.168.xxx.yyy, classed-only network software will set the network mask to be equivalent to 255.255.255.0 (or /24). 
Today most network software ignores the class of the network and will require a network mask for all ip number blocks. For instance, you can use 192.168.0.0 to 192.168.3.255 as a single classless subnet containing 1024 ip-addresses if you use network mask 255.255.252.0

