On Sat, 08 Jan 2005 12:47:52 -0500, Peter Hansen <[EMAIL PROTECTED]> wrote:
>Paul Rubin wrote: >> When Unix was first written, people thought implementing an OS in C >> was ludicrous. Everyone knew OS's had to be written in assembler. > >Actually, when Unix was first written that belief was entirely >correct, and OSes *did* have to be written in assembler. > >That is, pure C did not have the capability to handle all >that was required. I recall it taking a good decade before it >became *common* to find C compilers with, for example, @interrupt >support to let the compiler generate code that properly saved >all registers and used RTI instead of RTS (or whatever it might >have been called one one's particular flavour of CPU). > >Now, once you added a few tiny interrupt handlers, and some context >switching (stack manipulation) routines, pretty much everything else >*could* be done in C, but that doesn't invalidate the point. > >I think it's safe to say that none of pure C, pure Lisp, or pure Python >are really capable of being used as the *sole* language to build >an operating system. > >It's also safe to say that this is a largely irrelevant point. >It would probably only be of academic interest to try to do >something like that. Any practical attempt would not think more >than twice of resorting to a little "glue" in assembler or in >the form of "canned" byte sequences built by hand and stuck >into the appropriate places in memory... Well, usually there's more than one tool in the chain from source to bootable loader and OS image, even if you are writing in C and assembler, and there's usually more to an OS than the bootable image contains. So ISTM "writing an OS in <language>" is pretty loose talk ;-) Regards, Bengt Richter -- http://mail.python.org/mailman/listinfo/python-list
