In this fashion, MRP assists operation managers in planning and controlling inventories by answering the basic questions of what to order, how much to order, when to order and when the delivery should be scheduled.
This is achieved by looking at future requirements for the finished products and it uses this, and other information, to produce statements on sub-assemblies, components and raw materials necessary to complete the end products.
The three major inputs of a MRP system are the Master Production Schedule (MPS), the Bill of Materials (BoM) and the inventory status records (or Inventory File). Without these basic inputs the MRP system cannot function.
Figure 3: Typical MRP System