reserve a, b, c, a1, a2, b1, b2 for Int-Location,
  l, l1, l2 for Nat,
  f, g, f1, f2 for FinSeq-Location,
  i, j for Instruction of SCM+FSA,
  X, Y for set;

theorem Th18:
  i = a :=len f or i = f :=<0,...,0>a implies UsedIntLoc i = {a}
proof
  reconsider ab = {a} as Element of Fin Int-Locations by FINSUB_1:def 5;
  assume
A1: i = a :=len f or i = f :=<0,...,0>a;
  then InsCode i = 11 or InsCode i = 12 by SCMFSA_2:28,29;
  then UsedIntLoc i = ab by A1,Def1;
  hence thesis;
end;
