HP 3000 Manuals

HP Transact Reference Manual

Input Register 

The input register contains a character string entered by a user in
response to a prompt generated by the INPUT verb.  Typically, the
contents of the input register are tested with an IF verb for a yes or no 
condition.  Because the processor upshifts all responses, it is not
necessary to test for "YES" and "yes", for example.  The contents of the
input register cannot be assigned to any data item or any other register.

MPE/iX 5.0 Documentation