Complex sentence: In multi-programming or in multi-user environment it is common for many users to be executing the same program if individual copies of these programs were given to each user, much of the primary storage would be wasted.
Split into simpler sentences: In multi-programming or in multi-user environment it is common for many users to be executing the same program. If individual copies of these programs were given to each user, much of the primary storage would be wasted.