Application Cursor Keys mode is a way for the server to change the control sequences sent by the arrow keys. In normal mode, the arrow keys send ESC [A
through to ESC [D
. In application mode, they send ESC OA
through to ESC OD
.
Application Cursor Keys mode can be turned on and off by the server, depending on the application. PuTTY allows you to configure the initial state.
You can also disable application cursor keys mode completely, using the ‘Features’ configuration panel; see section 4.6.1.