By extending Ken Thompson's B compiler. The B compiler was initially written in ...

By extending Ken Thompson's B compiler. The B compiler was initially written in TMG before Thompson rewrote it in B. Then Richie added types like 'char' and 'int' and called it NB ("new B"), then he added structs and C was born.

The TMG interpreter used by Thompson to create B was implemented for the PDP-7 by Doug McIlroy in PDP-7 assembly language: http://minnie.tuhs.org/pipermail/tuhs/2014-September/005149....

This is what TMG looked like: http://multicians.org/tmg.html