    MEM(IV)                      5/27/74                      MEM(IV)

    NAME
         mem, kmem, null  -  core memory

    DESCRIPTION
         Mem is a special file that is an image of the core memory of
         the computer.  It may be used, for example, to examine,  and
         even to patch the system using the debugger.

         A memory address is an 18-bit quantity which is used direct-
         ly as a UNIBUS address.  References  to  non-existent  loca-
         tions cause errors to be returned.

         Examining and patching device registers is likely to lead to
         unexpected results when read-only  or  write-only  bits  are
         present.

         The  file kmem is the same as mem except that kernel virtual
         memory rather than physical memory is accessed.  In particu-
         lar,  the  I/O  area  of kmem is located beginning at 160000
         (octal) rather than at 760000.  The 1K region  beginning  at
         140000 (octal) is the system's data for the current process.

         The file null returns end-of-file on read and ignores write.

    FILES
         /dev/mem, /dev/kmem, /dev/null

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