B was a small systems programming language created by Ken Thompson at Bell Labs around 1969, in the period just after Bell Labs withdrew from the Multics project and Thompson began building Unix. In his history “The Development of the C Language,” Dennis Ritchie traces the line from BCPL through B to C, explaining that the team had used BCPL and regretted losing its advantages when working closer to the machine.
Ritchie’s account gives the most memorable description of where B came from. He writes that “B can be thought of as C without types; more accurately, it is BCPL squeezed into 8K bytes of memory and filtered through Thompson’s brain.” Like BCPL, B was typeless: it worked with machine words and left interpretation up to the program.
B was used on the early Unix machines, including the small DEC computers of the time. Its typelessness was a real limitation as the team tried to handle different kinds of data and the byte-addressed PDP-11, which made the lack of distinct data types awkward.
The response to those limitations was C. Ritchie evolved B by adding a type system and other features, producing a language that kept B’s directness while gaining the structure needed for serious systems work. B itself faded, but as the bridge between BCPL and C it occupies a key place in programming history.