bzs@bu-cs.bu.EDU (Barry Shein) (06/21/87)
Re: What's a kernel Well, it depends. I can't remember who said it but I remember a definition of an operating system as being a method of assigning new, possibly more useful, names for objects within a hardware system. Thus disk addresses become files, interrupts become signals etc. as services are indirectly requested through an operating system's kernel. It is the software which provides names and other abstractions for the hardware objects which comprise the total system. Another definition, which might be more conventional, is that software which is (plus or minus hackery) only enterable via a highly structured trap service routine (indirect vs direct call) is the kernel proper for systems which employ monolithic monitors. Most O/S's provide this (IBM OS's SVC, CMS's DIAGNOSE, Unix's TRAP or similar mechanism [was it IOT on the PDP-11?], RT11's EMT, TOPS-20 JSYS, etc etc.) Some muddy it by mapping pieces of the kernel code into the user space (VMS's RMS) but that also muddies the question of whether this code is really part of the kernel, or just a form of shared library (application) code. See, for example, Deitel, H.M., "An Introduction to Operating Systems", Addison-Wesley, 1983, pp. 65. for a discussion of Monolithic Monitors (kernels) vs other approaches. Remember, when answering questions about operating systems all statements must begin with: "Well, it depends..." Cheers. -Barry Shein, Boston University