That IP address configuration screen in the MacOS of yesteryear was amazing, wow. The slider to select the number of host/network bits is slick. I wonder why we don’t have something like that today.
Because CIDR happened. The net/subnet/node nomenclature used by MacTCP is a relic of classful routing.
Today, it's much simpler to type /26 after your IP address instead of entering 255.255.255.192, or playing around with a non-standard host/network slider.
And it assumed a specific network architecture -- e.g, if you have a class A network, the middle two octets of your address represent a "subnet" and the last octet represents a "node". This may have been appropriate in pre-CIDR networks where all local nets were /24, but it's no longer true today; it's not uncommon to have networks which split on non-octet boundaries.
- That there were 4 octets in an IP address.
- Class-based IP addressing.
- Subnet bit masks.
The UI that replaced it was an improvement in that all it asked for was a series of numbers, separated by dots, constrained to 0-255.