Terminal I/O should normally be done using the ADAM parameter system PAR_ and message system, MSG_ with the final output being performed by the ASTERIX extension to this , MSG_PRNT. Bulk data are generally stored and accessed via HDS but if files are used then logical unit numbers should be obtained using FIO_GUNIT and freed after use by FIO_PUNIT; these are found in FIO_LIB/LIB. PRINT statements should only be used for debugging.