Spacewar 2B

There are two different known versions of Spacewar 2B:

1) The authentic source code from 25 Mar 1962:
http://www.masswerk.at/spacewar/sources/spacewar_2b_25mar62.txt

2) The reconstructed source code of the two binary tapes
"spacewar2B_2apr62.bin" [1] and "spaceWar_SA-5.bin" [2]:
http://www.masswerk.at/spacewar/sources/spacewar_2b_2apr62.txt


The only differences in these files are regarding to the polarity of
the sense switch settings.

The version from 2 April 62 uses the more commonly known settings:

   SSW 1 UP: INERTIAL ROTATION
         DOWN: BERGENHOLM ROTATION
   SSW 2 UP: LIGHT GRAVITY
         DOWN: HEAVY GRAVITY
   SSW 3,4
         00: MOVING STARS, NORMAL
         01: MOVING STARS, FAST
         10: STATIONARY STARS
         11: NO STARS
   SSW 5 UP: HEAVY START TRAP
         DOWN: HEAVY STAR TO ANTIPOINT
   SSW 6 UP: NO HEAVY STAR
         DOWN: HEAVY STAR ON

whereas the the authentic source from 25 March 62 uses a generally
switched polarity (on/off) for interpreting these settings.

Source formats are as for the "macro1,.c" assembler for UNIX systems
using a prefix backslash ("\") to indicate a variable name with an
upper stroke.

Spacewar! was conceived in 1961 by Martin Graetz, Stephen Russell, and Wayne
Wiitanen. It was first realized on the PDP-1 in 1962 by Stephen Russell,
Peter Samson, Dan Edwards, and Martin Graetz, together with Alan Kotok, Steve
Piner, and Robert A Saunders. — Spacewar! is in the public domain, but this
credit paragraph must accompany all distributed versions of the program.


N. Landsteiner
2014-08-22


[1] http://www.bitsavers.org/bits/DEC/pdp1/papertapeImages/20050823/spacewar2B_2apr62.bin
[2] http://www.bitsavers.org/bits/DEC/pdp1/papertapeImages/20031202/InsidePDP1_80s_box3/spaceWar_SA-5.bin