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


     mem  -  core memory


     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

     directly  as  a  UNIBUS address.  References to non-existent

     locations 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


     The file kmem is the same as mem except that kernel  virtual

     memory   rather   than  physical  memory  is  accessed.   In

     particular, 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.


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