function pg=abcpgchk(a,b,c)
%ABCPGCHK  Check A, B, C for a pure gain block
%       ABCPGCHK returns 1 if A, B and C are all zero
%       and A is 1 by 1.
%       This is the representation of a pure gain in
%       state space form.   D contains the gain.

%       Dr M.P. Ford 23rd August 1987
% Copyright (c) 1987 by GEC Engineering Research Centre & Cambridge Control Ltd

if max(size(a))==1
   if a==0 & ~any(b) & ~any(c)
      pg = 1;
   end
else
   pg = 0;
end