entical fields, where 
    all of the fields are themselves arrays,
          
       C{1}.F1=A11, C{1}.F2=A12, ... , C{1}.FN=A1N
       C{2}.F1=A21, C{2}.F2=A22, ... , C{2}.FN=A2N
          :        :        :        :        :
       C{M}.F1=AM1, C{2}.F2=AM2, ... , C{M}.FN=AMN
    
     and where all the AMN for any particular field (F1,say), have the same
     number of columns, that is, SIZE(A11,2)=SIZE(A21,2)= ... =SIZE(AM1,2).
 
     S=<a href="catstruct.html">CATSTRUCT</a>(C) then returns a structure