reserve F for total
  NAT-defined (the InstructionsF of SCM)-valued Function;

theorem Th4:
  for k, n being Element of NAT, s being State of SCM,
    a, b being Data-Location st
  IC Comput(F,s,k) = n & F.n = a := b
 holds IC Comput(F,s,k+1) = n+1 &
  Comput(F,s,k+1).a = Comput(F,s,k).b &
  for d being Data-Location st d <> a
   holds Comput(F,s,k+1).d = Comput(F,s,k).d
proof
  let k, n be Element of NAT, s be State of SCM, a, b be Data-Location;
  assume
A1: IC Comput(F,s,k) = n;
  assume
 F.n = a := b;
  then Comput(F,s,k+1)
   = Exec(a:=b, Comput(F,s,k)) by A1,Lm2;
  hence thesis by A1,AMI_3:2;
end;
