There are two main methods for accessing functions by keyboard, the access characters and the function keys. The R/3 System provides another keyboard access method based on access characters, the fastpath. Furthermore, on certain computer platforms like Windows™ or Motif you can even access pushbuttons with the keyboard.
Access Characters and Fastpaths
Functions may be called from the keyboard via their mnemonic access characters. You access a function by pressing the ALT key in combination with the respective access character. The access character is shown in the pull-down menu as an underlined character. Underlining is done automatically once you defined an access character in the Menu Painter. For the standard functions the Menu Painter proposes access characters that conform to the SAP Style Guide. For other functions you have to choose the access character yourself. Make it unique (within a pull-down menu) and typical for the function. Often you can use the first character of the function name. If it is already used, try to find one that is easily associated with the function.
Access characters also represent a possible path, the so-called fastpath, for starting a task or initiating an action. To do this, you have to enter a period into the command field followed by a string of access characters. The sequence of access characters you enter in the command field begins with the menu bar item itself and ends with the desired function. It corresponds to the sequence of menu options you would have to choose with the mouse in order to initiate the desired action. Note that this, too, is a is a keyboard access mechanism for the function.
Function keys are another very fast and convenient keyboard access mechanism for functions, but with some differences to the preceding mechanisms. Function keys are special keys on a keyboard that are reserved for certain application functions. Therefore they are not mnemonics! As the number of function keys on a keyboard is limited, you have to observe some restrictions. In addition to pressing a function key these functions can be accessed via the function key menu. This menu pops up when the user depresses the right mouse button. The R/3 System supports up to 99 (V1-V99) function keys that are in part accessed via mnemonic shortcuts.
There is one important point to be observed: If you want to assign a pushbutton to a function which is located in the standard or application toolbar, you have to assign a function key to it first. In other words: You can only assign pushbuttons in the toolbars to functions with function keys assigned to them.
Every function key belongs to one of the following four function key groups:
Look at the SAP Reference Lists on the SAP User Experience Community for function keys, the list of virtual keys and the function assignments to virtual keys.
For the sake of consistency within an application, try to use standard function keys for functions active in several tasks of the application.
Source: SAP R/3 Style Guide