This function may be performed alone by calling the script with entrystage and finalstage=`addbits'. Added to the list of detected sources are (i) a keyword SKY_AREA which records the total area in square degrees of the area of non-zero exposure; (ii) columns STREAM_N and FIELD_N which record the values passed into the streamnumber and idnumber parameters. For the latter columns, all rows have of course the same value: they become useful only when several lists are merged during processing by eimsimreduce.