Complex sentence: A horizontal bar hides either all the complement numbers when it is slid to the top or all the direct numbers when it is slid toward the center of the machine and thereby displays either the content of the accumulator or the complement of its value.
Split into simpler sentences: A horizontal bar hides either all the complement numbers when it is slid to the top, or all the direct numbers when it is slid toward the center of the machine. It thereby displays either the content of the accumulator or the complement of its value.