The code for the part of the program calling unit 10:
**************
OPEN MAIN FILE
OPEN(UNIT=10,FILE=mainfile,STATUS='OLD',ACCESS='DIRECT', !hl1
*recl=81,FORM='FORMATTED' ) !hl1
c *COUNTBY='RECORD',FORM='FORMATTED',IOSTAT=ISTAT)
C
C READ LAST DATE FROM MAIN FILE, INPUT...