Classic MacOS in the 80s had "MPW" macintosh programmers workshop - that treated open text windows as files and selections within the windows as files, so it wa

Classic MacOS in the 80s had "MPW" macintosh programmers workshop - that treated open text windows as files and selections within the windows as files, so it wasn't uncommon to have a portion of an otherwise documentation file have a "click here and hit enter", which would use the selected text as stdin for some semi-ported unix tool. (no memory protection or multitasking, so true pipelines with backpressure didn't work)