Bill Gates and Paul Allen develop software for the MITS Altair using a PDP-8/E.
Year of feature (shown above)
Firstly, it is completely unrealistic for two college kids to have their own private PDP-8/E. If a PDP-8/E was cheap enough for two college kids (even Harvard students) to afford, the Altair would've been dead before it was even conceived of.
Secondly, Gates and Allen developed the Altair 8800 BASIC using a PDP-10 that Gates had access to due to work related reasons.
Thirdly, there are no peripherals for the PDP-8/E show, and it looks like there aren't any peripherals attached (to what looks like a pretty full system) either.
Lighten up FRANCIS