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.TH MEM 4 "9 February 1983"
.UC 4
mem, kmem \- main memory
.I Mem
is a special file that is an image of the main memory
of the computer.
It may be used, for example, to examine
(and even to patch) the system.
Byte addresses in
.I mem
are interpreted as physical memory addresses.
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 present.
The file
.I kmem
is the same as 
.I mem
except that kernel virtual memory
rather than physical memory is accessed.
On PDP11's, the I/O page
begins at location 0160000 of
.I kmem
and per-process data for the current process
begins at 0140000.
On VAX 11/780 the I/O space begins at physical address 20000000(16);
on an 11/750 I/O space addresses are of the form fxxxxx(16); on all VAX'en
per-process data f\&or the current process is at virtual
On PDP11's and VAX's, memory files are accessed one byte
at a time, an inappropriate method for some
device registers.