I wrote a Battleship game in PL/I on a Univac 1100 ca. 1978. It was a pretty cool language, but those /* comments */ felt weird after FORTRAN and COBOL.
I used PL/UM, a PL/I variant at the University of Maryland at about the same time. Also on a Univac 1100, specifically an 1108 and/or 1106. Where you there, too?