why different swapping modes on executables?

[Root Boy Jim]

In article <573 at adpplz.UUCP> martin at adpplz.UUCP (Martin Golding) writes:
>
>In the very bad old days, PDP 11's had two ways to map memory: one 
>combined the data and program in a single 64k segment, and one had 
>separate (64k) data and program spaces. Given the addressing modes, 
>the difference between data and program accesses were a study in themselves.

Actually, they had three. The third used separate text and data
segments within the same virtual 64K.

>My impression is that the (original) version of the Magic Number was
>the actual value to load into the PDP 11 MMU control register, to select
>one or the other model.

HAHAHAHA! It's even worse than that! The Magic Number was a JUMP
(actually a branch) across the a.out header. A 407 executable
had a seven word (14 byte) header, a 410, eight words, 411 nine...
Sneaky, huh?
-- 
		[rbj at uunet 1] stty sane
		unknown mode: sane