UnFact: The M4, originally the London-South Wales Macro Processor, is included in most Unix-like operating systems, and is a component of the POSIX standard. The English section of the language was written between 1961 and 1971; while the Welsh element was largely completed by 1980.
The part of the program from London to Bristol was designed by Brian Kernighan and Dennis Ritchie, and runs closely in parallel with the A4*.
* See: ISO 216, A series paper, A4.










