theorem
  for i being Instruction of STC N st InsCode i = 1 holds i is non halting
proof
  let i be Instruction of STC N;
  set M = STC N;
  set s =the  State of M;
  assume InsCode i = 1;
  then
A1: Exec(i,s).IC M = IC s + 1 by Lm3;
  assume for s being State of M holds Exec(i,s) = s;
  then Exec(i,s).IC M = IC s;
  hence thesis by A1;
end;
