This specification describes the functionality of the services provided by text terminal unit (TTU) services under XFS, by defining the service-specific commands that can be issued, using the WFSGetInfo, WFSAsyncGetInfo, WFSExecute and WFSAsyncExecute functions. This section describes the functions provided by a generic Text Terminal Unit (TTU) service. A Text Terminal Unit is a text i/o device, which applies both to ATM operator panels and to displays incorporated in devices such as PIN pads and printers. This service allows for the following categories of functions: - Forms oriented input and output - Direct display output - Keyboard input - LED settings and control All position indexes are zero based, where column zero, row zero is the top-leftmost position. If the device has no shift key, the WFS_CMD_TTU_READ_FORM and WFS_CMD_TTU_READ commands will return only upper case letters. If the device has a shift key, these commands return upper and lower case letters as governed by the user's use of the shift key.