AbstractA complex executive may be written as a core of minimum size, plus processes indistinguishable from those run by normal system users except for heavily circumscribed special privileges. Such an executive defines its virtual machine in a recursive fashion, since the processes abide by rules they help to enforce, and is ‘user‐like’ because most executive processing takes places in the protected, user mode. The advantages of such an executive are compactness because of lack of duplication of user and executive routines, good documentation because the user‐process interface is well defined and stable and, most important, excellent protection of the system from the executive itself, which utilizes all of the hardware protection available whenever possible.Situations most appropriate for the user‐like technique are described, and a series of detailed examples is given to show its application to a multiprogramming executive's memory allocatio
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