Read-only memory (ROM) is a semiconductor integrated circuit that functions as a computer device for the permanent storage of data and programming instructions. Once it is prerecorded at the time of manufacture the ROM can be read randomly but cannot be modified. A ROM memory device is made when a design company provides a semiconductor manufacturer with the instructions or data that is to be stored, and then the manufacturer makes the specified devices according to those specifications. Since making memory devices is an expensive procedure, ROM devices are almost always made in very large quantities. Before making ROM devices, experimental designs are created in small quantities using PROM (programmable read-only memory) or EPROM (erasable programmable read-only memory). The evolved definition of ROM has expanded to also include forms of memory that can be modified, but generally only under particular circumstances, so that, in...