Complex sentence: The machine would store numbers in memory units, and there would be a form of sequential control, that is, one operation would be carried out before another in such a way that the machine would produce an answer and not fail.
Split into simpler sentences: The machine would store numbers in memory units, and there would be a form of sequential control. This means that one operation would be carried out before another in such a way that the machine would produce an answer and not fail.