Most of the contacts on the MK are registers?

Question

Electronics

Good afternoon, tell me, I'm reading about assembler and there are 4 main recording registers and a bunch of others.
This is about the legs of the MK, i.e. 4 registers A, B, C, D, which are each divided into 2 by 4 bits, these are the inputs 0-7D per μ for recording, and 0-7S, which are for output, these are also registers, but for a different purpose (output) ?
And why are there only 4 main ones for recording even in modern processors, where there are many times more of these legs than in MK?

Answer 1

And why are there only 4 main ones for recording even in modern processors, where there are many times more of these legs than in MK?

So look modern MK.
Here, for example, 11 I / O ports and each port can have up to 16 output pins .
And do not confuse the port with pins and its registers.
The state of the pins can be determined not by one register, but by a whole group.
The number of ports, specific registers that control the I / O ports depend on the specific MK.
It is impossible to answer your case without knowing which MK you are talking about.
In general , registers are responsible for the port(several) that determine the operation of the port pins: work for input or output, determining the mode of operation of digital or analog, registers that allow you to bring certain peripherals of the MK to your feet (alternative functions), etc. It makes sense to consider a specific MK in more detail and dance from it. In the general case, it is all the same, but in each specific MK there may be differences in the number of registers and their functionality.