ANY FILE ON DSK OR DTA HAS A NAME WHICH LOOKS LIKE FFFFFF.XXX WHERE FFFFFF
IS THE FILENAME AND XXX IS THE EXTENSION.  SOME STANDARD EXTENSIONS ARE:
REL=RELOADABLE MACHINE-LANGUAGE PROGRAM		DMP=CORE IMAGE PROGRAM
FAI=ASSEMBLY-LANGUAGE SOURCE PROGRAM (FAIL)	MAC=ASM-LANG S.P.(MACRO)
SAI=ALGOL(SAIL)  OSA=OLD SAIL (BACKUP)  F4=FORTRAN IV  LSP=LISP
DAT=FORTRAN OUTPUT DATA  TXT=ENGLISH TEXT  MAN=MANUAL