PF keys
The function keys F1 to F24, which carry the main actions on a mainframe screen: help, exit, save, page up and down.
Also written function keys, PFK
PF keys, short for program function keys, are how you act on a mainframe screen. With no mouse and no menus to click, the function keys carry the verbs.
A common set is nearly universal across ISPF and most mainframe tools. F1 gives help, F3 exits the current screen and goes back, F7 and F8 page up and down, F10 and F11 scroll left and right, and F12 cancels. Sites and applications can change them, and most screens show the current assignments somewhere on the display.
Two are worth committing to memory immediately. F3 is how you get out of anywhere, and pressing it repeatedly will eventually return you to the main menu. F1 is help, which on ISPF is context-sensitive and actually useful.
Because a 3270 screen only transmits when you press a transmitting key, pressing a PF key is also what sends everything you have typed. That is why nothing appears to happen until you press one.
Related terms
- Green screenThe text-only, keyboard-driven interface most mainframe work happens through, named after the green phosphor of early terminals.
- 3270 terminalThe classic mainframe display device, and the protocol still used today to talk to z/OS over a network.
- ISPFThe full-screen, menu-driven workbench most people use to do their day-to-day work on z/OS.
- ISPF editorThe full-screen text editor used to write and change JCL, COBOL, REXX and anything else held in a dataset.