[TUHS] B Language revived on V4 Unix

[Paul Ruizendaal via TUHS]

> Date: Sun, 19 Apr 2026 22:49:03 -0400
> From: Douglas McIlroy
> Subject: [TUHS] B Language revived on V4 Unix
> 
> The feature of B that most impressed me was not its size, but the fact
> that it could compile (and run!) code that was too big to fit in
> memory, thanks to software paging. In particular, when a new feature
> caused the compiler to become too big, it could still run. Then it
> could be modified to exploit the new features to shrink it back.
> 
> So bringing full B up on v4 is nice, but not such a tour de force as
> it was on v1.
> 
> Doug

I had not heard of that feature before. Is this referring to early B on the PDP-11 or to B on the PDP-7? (“on v1” suggests the former).

Could you elaborate on the “paging” aspect? If I remember well, on v1 there was only a simple “high-low” memory management system, and as you call it “software paging” I assume you are not referring to that. My first (wild) guess would be that you refer to some type of overlay system, managed by the B runtime library. Maybe somewhat similar to the overlay system that was later included in the C compiler as it evolved on 2BSD?

As always, I am aware that I’m inquiring about details from 50+ years ago and that answers may be lost to the mists of time.

Paul