/sys$common/syshlp/helplib.hlb Lexicals, F$CVUI, Example  *Conan The Librarian (sorry for the slow response - running on an old VAX)

  $ A[0,32] = %X2B
  $ SHOW SYMBOL A
    A = "+..."
  $ X = F$CVUI(0,4,A)
  $ SHOW SYMBOL X
    X = 11   Hex = 0000000B  Octal = 00000000013

      This example uses an arithmetic overlay to assign the
      hexadecimal value 2B to all 32 bits of the symbol A. The
      symbol A has a string value after the overlay because it was
      previously undefined. (If a symbol is undefined, it has a
      string value as a result of an arithmetic overlay. If a symbol
      was previously defined, it retains the same data type after
      the overlay.) The hexadecimal value 2B corresponds to the ASCII
      character "+".

      Next, the F$CVUI function extracts the low-order 4 bits
      from the symbol A; the low-order 4 bits contain the binary
      representation of the hexadecimal value B. These bits are
      converted, as a signed value, to an integer. The converted
      value, 11, is assigned to the symbol X.