Add to ORKGAbstract: Until about 1970, programming languages and their compilers were perhaps the most active system software area. Due to its technical position at that time, IBM made significant contributions to this field. This retrospective concentrates on the two languages Algol 60 and PL/I, because with them compiler development reached an historical peak within IBM's European laboratories. As a consequence of IBM's "unbundling" decision in 1969, programming language activity within IBM's European laboratories decreased considerably, and other software activities were initiated. Much knowledge about software development was acquired from this early language activity. Some of the lessons learned are still useful today