Either the input or the display area can be used as the edit area. Often the number of lines in an input string exceeds the number of lines available in the edit area display. When the input string is longer than the input area, the UP command is used to generate additional lines into which to enter commands. The edit area is used as a window into the input. The UP command moves this window up over the input.
The UP command is not effective when the first line of the input string is the last line in the edit area (that is, the beginning of the input string is reached).
If the input area is the edit area, the UP command can only be executed by PF21 key, or a user-assigned PF key.