OneDbf:Struc: read-only: array
  Database structure (the structure of the fields) is stored here
  Struc:={}
  AAdd( Struc, {cFieldName,cFieldType,nLen,nDec} )
  ...
  Where:
  cFieldName - is the fieldname
  cFieldType - can be "C","M","N","D","L"
  nLen       - field size in number of characters
  nDec       - number of decimal places of type "N", or type "C" size
               extension in 256 multiples (see clipper manuals)
  The structure of the array Struc is the same as the aStruc in clipper
  function DBCREATE().