Re: Why are Ada compilers difficult to write ?

[Dennis Lee Bieber <wlfraed@ix.netcom.com>]

On Fri, 22 Jun 2018 19:54:59 -0700 (PDT), "Dan'l Miller"
<optikos@verizon.net> declaimed the following:

>
>Yes, but the Z80 has the 8080's three 16-bit registers BC, DE, and HL by concatenating 8-bit register pairs, but the Z80 has three more shadow 16-bit registers BC', DE', and HL' that can be swapped in and out.  (Plus AF and AF' if you like living dangerously with the flag registers.)  6502 needed the page-zero trick because its register-set was so spartan.  (Only TI's TMS9900 had an even more spartan register-set in that era.)
>

	As I recall, for all practical purposes, the 9900 did not have general
purpose registers -- it had a "register pointer" into RAM (Just checked --
"Workspace Pointer" to 16 16-bit "registers" located in RAM). The other two
"real" registers were the program counter and status.

	In essence, general purpose registers were indexed indirect addresses.


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	Wulfraed                 Dennis Lee Bieber         AF6VN
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