There is no one PDP-1 Source code it turns out.<p>It's complicated. Check here.
<a href="https://www.masswerk.at/spacewar/sources/" rel="nofollow">https://www.masswerk.at/spacewar/sources/</a><p>Check out a real deep dive into the source code and by default the PDP-1
<a href="https://www.masswerk.at/spacewar/inside/" rel="nofollow">https://www.masswerk.at/spacewar/inside/</a><p>This awesome work is all courtesy of Norbert Landsteiner of mass:werk
<a href="https://www.masswerk.at/info.php" rel="nofollow">https://www.masswerk.at/info.php</a><p>Explore the site, there's also a Space War emulator and a re-implementation in javascript.