/sys$common/syshlp/helplib.hlb FORTRAN, Format Specifiers, L  *Conan The Librarian (sorry for the slow response - running on an old VAX)

  Lw (Logical Editing)

  On input, transfers "w" characters from the external field and
  assigns a logical value to the corresponding I/O list element
  (which must be integer or logical data type).  If the first
  nonblank characters of the field are T, t, .T, or .t, the value
  .TRUE. is assigned to the corresponding I/O list element; if the
  first nonblank characters are F, f, .F, or .f, the value .FALSE. is
  assigned.  An all blank field is assigned the value .FALSE.  Any
  other value in the external field produces an error.  The logical
  constants .TRUE. and .FALSE. are acceptable input forms.

  On output, transfers either the letter T (if the value of the
  corresponding I/O list element is .TRUE.) or the letter F (if the
  value is .FALSE.) to an external field that is w characters long.
  The letter T or F is in the rightmost position of the field,
  preceded by w-1 spaces.