Getting started

James J. Besemer jb at cascade-sys.com
Sun Sep 29 09:35:38 CEST 2002


David LeBlanc wrote:

>In fact, the names of some Lisp funtions came from the machine registers of
>the same name: car (current address register) and cdr (current data
>register) are the only ones I recall offhand.
>

Yup.  It was from IBM's 709/7094 computer.

Some Lisps had a 3rd, "CSR" but I don't recall the name of the register. 
 Status?  Subroutine?

Being able to branch in yet a third direction did not add as much 
utility as the first two.  And it didn't translate as well to most other 
architectures.  

It was nevertheless implemented in one CDC Lisp I am aware of, where 60 
bit words and 18 bit addresses left plenty of room for 3 addresses (with 
bits left over) in a cell.

--jb

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