He mentions that it can easily be shown using the elements of recursive functions that every number calculable on the arithmetic machine is computable. A proof of which was given by Lambek on an equivalent two instruction machine : X+ (increment X) and X− else T (decrement X if it not empty, else jump to T).
He mentions that it can easily be shown using the elements of recursive functions that every number calculable on the arithmetic machine is computable. A proof of which was given by Lambek on an equivalent two instruction machine  X+ (increment X) and X− else T (decrement X if it not empty else jump to T)