DISK I/O

I would do it like this:

1. Change the definition of FN myGetWDrefNumFromAlias% so that it only takes theAliasNum% parameter (remove the itemType% parameter)

2. Inside the FN, after the "LONG IF myErr% = _noErr" line, add this line:

    itemType% = FN WhatType(fsSpec)

Here's the WhatType function, which will return the type. (Caution: it's untested):

LOCAL FN WhatType(@fsSpecAddr&)
  DIM fSpec;0, fVrefNum%, fParID&, 63 fileName$
  DIM pb.108
  fSpec;70 = fsSpecAddr&
  pb.ioNamePtr& = @fileName$
  pb.ioVRefNum% = fVrefNum%
  pb.ioDirID& = fParID&
  pb.ioFDirIndex% = 0
  OSErr% = FN GETCATINFO(@pb)
  SELECT CASE
    CASE OSErr% < 0
      theType = OSErr%  'return error code
    CASE (PEEK(@pb.ioFlAttrib) AND BIT(4)) = 0
      theType = _isFile
    CASE ELSE
      IF pb.ioDrParID& = 1 THEN theType = _isDisk ELSE theType = _isFolder
  END SELECT
END FN = theType