The file /dev/mem
is an interface to the physical memory
of the computer. Byte offsets in this file are interpreted as physical memory
addresses. Reading and writing this file is equivalent to reading and writing
memory itself. An error will be returned if an attempt is made to reference an
offset outside of /dev/mem
Kernel virtual memory is accessed via the file
/dev/kmem in the same manner as
/dev/mem. Only kernel virtual addresses that are
currently mapped to memory are allowed.
On the alpha, physical memory may be discontiguous; kernel virtual memory begins
Writeability of these devices is controlled by the system
The /dev/mem and /dev/kmem files
appeared in Version 6 AT&T UNIX.