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

  IBITS (integer, start-position, length)

  A function that returns the value of the bits of the
  first argument specified by start-position and number
  of bits.  The low-order bit is position 0.

  +------+---------+----------+------------+-------------+
  | Args | Generic | Specific |  Argument  | Result Type |
  +------+---------+----------+------------+-------------+
  |  3   |  IBITS  | IIBITS   | INTEGER*2  | INTEGER*2   |
  |      |         | JIBITS   | INTEGER*4  | INTEGER*4   |
  +------+---------+----------+------------+-------------+