LGP-21 and LGP-30 memory, number, address explained

[Tom Jennings]

These machines have a peculiar (to me) memory format, it's not really
obvious, so I worked it out and wrote it up here

http://wps.com/projects/LGP-21/Documentation/arithmetic.html


simh adds to the confusion, somewhat, because it displays memory by
default in "normal" mode. e -m address does the right thing for
instructions, but it's missing a -option to display numerical data; for
example a "2" stored in LGP memory shows as "4" in simh because of the
spacer bit.

Memory is 31 bits wide, the accumulator is 32 bits...