Windows convention for access keys (as opposed to keyboard shortcuts). E.g. you can choose &File > &Open by pressing Alt-F then O (as an alternative to Ctrl-O), with the requisite keys underlined when you press Alt; you can choose the dialog option labelled &Abort by pressing Alt-A, with the requisite key always underlined in the traditional Win32 toolkit. (By convention, OK and Cancel don’t get access keys, as you can always use Enter and Escape respectively instead.) Not every menu item gets a shortcut, but in a competently designed Windows UI every one gets an accelerator.

(This idea is nice but not without its problems. For those of us who regularly use more than one keyboard layout or even system locale, it doesn’t work all that well.)