dsw: pdp7 memorabilia

[dmr at research.UUCP]

I happened to dredge up an old notebook and found a listing
of the PDP-7 version of dsw.  Because several people have approached
me recently about reviving a version of PDP-7 Unix as a sort of
paleontological exhibit, and because the subject has been discussed
here, I thought people might be interested in seeing the code.
I first considered net.sources, but decided not to carry whimsy too far.

		Dennis Ritchie

Notes:

1) The assembler has Knuth-style temporary labels but no literals.

2) The name of the current directory was evidently ".."

3) Formatting is faithfully reproduced.

4) "sys save" makes a core image.
------
" dsw

   lac djmp
   dac .-1
   oas cla
   cma
   tad d1
   dac t1
   sys open; dd; 0
1:
   lac d2
   sys read; dir; 8
   sna
   sys exit
   lac dir
   sna
   jmp 1b
   isz t1
   jmp 1b

wr:
   lac d1
   sys write; dir+1; 4
   lac d1
   sys write; o12; 1
   sys save
do:
   sys unlink; dir+1
   sys exit

d1: 1
d2: 2
o12: 012
t1: 0
djmp: jmp do
dd: 056056; 040040; 040040; 040040
dir: .=.+8