dhesi@bsu-cs.bsu.edu (Rahul Dhesi) (05/31/89)
In article <24994@agate.BERKELEY.EDU> ked@garnet.berkeley.edu in comp.binaries.ibm.pc.d (Earl H. Kinmonth) writes: >I'm curious: why does TOPS20 seem to be going nowhere or am I mistaken >in this impression? In one sense TOPS-20 is going nowhere: DEC is supporting the DECsystem-20 family very, very reluctantly, and only because there are a lot of people who like the machine very much. Most of DEC's efforts in developing new software are directed towards VAX/VMS. TOPS-20 is a powerful operating system hidden behind a powerless command interpreter and relatively poor language support. However, there is so much third-party software available for TOPS-20 (including language translators, text editors, mail software, and modified versions of the command interpreter) that the whole package, properly configured, is very usable. People greatly like the command prompting feature of TOPS-20: At any point in a partially-typed command line you can ask TOPS-20 to complete a filename for you, or ask it to list possible things you can type at that point. Some of Columbia's implementations of Kermit, and some of the extras in today's csh and tcsh shells, are based on the TOPS-20 model. So while officially TOPS-20 can be considered to be obsolete and no longer being supported (not much, anyway), unofficially it seems likely to live on for a while. Its death will probably come when DEC stops providing maintenance for the hardware it runs on. Unfortunately the DEC-20 was really designed for assembly language programming and not for supporting high-level languages. It has a fairly orthogonal instruction set but has some funny features (like no condition flags, infinite levels of indirection, variable byte sizes, and a 36-bit word size) that might not make things easy for a compiler writer. At one time a machine called the Jupiter was widely publicized as DEC's successor to the DEC-20. This kept people from moving to other vendors while the VAX was developed. Some interesting insights into the DEC-20 architecture are described in one of the chapters of the book "Computer Engineering: A DEC View of Hardware Systems Design," by Bell, Mudge, and McNamara. (Aside: This is a slightly *biased* DEC view. As Tracy Kidder points out in "The Souls of a New Machine" about De Castro, the designer of the PDP-8, who was impertinent enough to leave DEC and go to work for Data General: "They expunged De Castro." The PDP-8 section in the book doesn't mention his name at all.) (Followups to comp.os.misc.) -- Rahul Dhesi <dhesi@bsu-cs.bsu.edu> UUCP: ...!{iuvax,pur-ee}!bsu-cs!dhesi Career change search is on -- ask me for my resume