Manufacturing networks provide the infrastructure to transmit manufacturing and management data used to define and control computer-integrated manufacturing systems or components of computer-aided design (CAD) and computer-aided manufacturing (CAM). These data consist of CAD drawings, production schedules, inventory information, production information, production programs (for example, computer-numerical control [CNC] and programmable logic control [PLC] programs), production order releases, operation sheets, routing sheets, production order releases, inventory levels, and maintenance information. The computer networks consist primarily of local area networks (LANs). LANs also can be joined to form enterprise-wide computing (EWC) or corporate intranets. An intranet is similar to the Internet except it can only be accessed by people within the company or organization. Regardless of the technology, the central issues of how to transmit data reliably over a distance at the highest appropriate speed (bits per second or bps) and at an economical cost (communications lines, hardware, software, and support personnel) remain constant. An operating system is the software that interfaces the user with the network and its components.