I did work experience at an IBM "shop" in the 80s, at a time when the PC and PC XT had just come out. They ran IBM minicomputers and used both 3270 terminals,

I did work experience at an IBM "shop" in the 80s, at a time when the PC and PC XT had just come out. They ran IBM minicomputers and used both 3270 terminals, and PCs fitted with an expansion card with a coax connection, to interface with the local mainframe, and the head office one (via some kind of expensive leased line). The 3270 had all the function keys "soft functions" on the 25th line. The terminal emulator on the PC had the same, and it was basically necessary for compatibility with the terminal applications they used. Being IBM, I have no doubt it was heavily standardised. Probably the precursor to Common User Access (CUA)?