ultrix man page for mem

mem(4)							     Kernel Interfaces Manual							    mem(4)

Name
       mem - physical main memory image

Description
       The is a character special file that is an image of the physical main memory of the computer.  It can be used, for example, to examine (and
       even to patch) the running system.

       Byte addresses in are interpreted as physical memory addresses.	References to nonexistent 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 present.

Restrictions
       The memory file is accessed one byte at a time. This may be inappropriate for some device registers.

Files
See Also
       MAKEDEV(8)

																	    mem(4)