The industry standard for computing support of MRP II implementations has been the traditional "closed-loop" material requirements planning (MRP) and Capacity Requirements Planning (CRP) system. In response to the problems of a previous generation of materials management practices, MRP emerged in the 1960s and came into widespread use. The output of the MRP process served as input for a CRP process.

These traditional MRP/CRP systems are still widely available today. They represented a major advance over the order point methods they replaced. Many companies have been significantly improved through their use.