How CPU's work (was Re: Hi, I'm new...)

[Don]

Dave McGuire wrote:
> Roy J. Tellason wrote:
>> The z80 added stuff I've never personally found all that useful 
>> otherwise,  and have never used the index registers (yet) or the 
>> alternate set,  all that much.
> 
>   I like the index registers; I use them with some frequency.  The 

IX and IY are great if you are used to writing code where you deal
with lots of struct's or diddle with stack frames.  For most
folks tinkering, they never figure out the value of them  :-(

> alternate register set, though...ugh.  It'd be much more useful if the 
> designers had provided a way to determine which set is currently in use!

Alternate registers are useful for interrupt handlers -- *if*
you ensure that they can't be nested.  You can cheat and
use AF in one IRQ and the other pairs (EXX) in another IRQ
(of course, assuming you only need AF in the one and don't
need A or F in the other!  :> )