                         IMP Core Environment Standard

                           Section 11: Miscellaneous

    *       constant name NIL

               The predefined pointer NIL may be used to terminate linked
            lists of items; any pointer variable which is pointing to NIL
            will have all its bits clear (0) {IAY: better wording required
            here, but see language implications section}.

    *       integer function SIZE OF ( name X )

               The number of storage units occupied by the given variable is
            returned.  The unit is machine dependent but is commonly a byte.

    *       integer function TYPE OF ( name X )

               This function returns a code which indicates the type of the
            object supplied as parameter.  The complete list of code values
            which may be returned by TYPE OF is as follows:

             0 - unknown type
             1 - integer
             2 - real
             3 - string
             4 - record
             5 - byte integer
             6 - short integer
             7 - long integer
             8 - long real
             9 - array
            10 - label