Service Manuals, User Guides, Schematic Diagrams or docs for : . Rare and Ancient Equipment cdc cyber cyber_180 IPLOS OS_Memos_1973-1975 19741120_OS_Structure

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                      ~(@]m                          THIS DOCUfolENT CONTAINS INFORHATION PROPRIETARY

                            ADVA            1        TO THE NATIONAL CASH REGISTER Cor'lPANY AND CONTROL
                                                     DATA CORPORATION, ITS CONTENTS SHALL NOT BE
                                                     DIVULGED OUTSIDE OF EITHER CO~'PANY NOR REPRODUCED
                                                     WITHOUT EXPlICIT PERHISSION OF THE DIRECTOR AND
                                                     GENERAL HANAGER, NCRICDC ADVANCED SYSTEr"S LABORATORY.
  DATE:         November 20, 1974
     TO:        R~'   E; Wagner                           LO(';ATION:   -   rbI\A~L.-




  FROM:         Ell C.. Crary        .-JZ-.-C <:!....--   LOCATION:         ESCASL                            EXT:   57
SUBJECT:        OS STRUCTURE-----'


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  Atter our discu~sions durin~ my last trip, I came away with the
  impression that some confusion exists concerning Address Spaces
  and their relationship to Processor States, Asynchronous Processing
  and Serialization of Access. Perhaps theconfusiQn~s only mine,
  but I would like to express my understanding of these concepts
  if for no other reason than to demonstrate its inadequacy and
  thus the need for further doc~mentation.
 Processor State is used to protect the OS environment from cor-
 ruption by errant code of a less trusted nature; in particular,
 to protect the OS from its user. In this context, the OS environ-
 ment is a collection of services upon which the user code may make
 requests. The user requests are normally of an explicit nature,
 but may be implicit as a result of some signal. A page fault is
 the most obvious case of an implicit service request.
 With the advent of mass storage and larger memories, t~e OS grew
 to include functions that are not services to be performed for
 the user code, but are jobs in their own right.' These System Jobs
 include spooling and job scheduling. A distinction ~ust be made
 between system jobs and services as;they are structured in a
 different manner within the framework of the OS.
 Address'Spaces are used to define jobs, or in some systems, job-
 ~teps.   The address space is the basic unit of accountability and
 the unit to which resources are assigned. With the inception of
 multi-programming, the address space also became a mechanism for
 relocation ..
 The tonfusion on the user of addr~ss space arises because it does
 not always have a complete definition or cause total relocation.
 We are apt-to lose si9ht of the relationship of the QSservices
 to the user code. But if address space is considered from the
 services point of view instead of the users, then we see that the
 u.er resides in the same address space ..
  R. E. Wagner                 -2-               November 20, 1974


    The point I wish 

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