Some drives can only read from discs, but commonly drives are both readers and recorders. Recorders are sometimes called burners or writers.Common media and technology families include CD, DVD, and Blu-ray Disc. Standalone, non-computer, optical storage devices also exist, for example popular CD players, DVD players, and some DVD recorders, but those are not covered in this article. Optical disc drives are generally used for small-scale archival or data exchange, being slower and more materially expensive per unit than the moulding process used to mass-manufacture pressed discs. But they—along with flash memory—have displaced floppy disk drives and magnetic tape drives in most cases because of the low cost of optical media and the near-ubiquity of optical drives in computers and consumer entertainment hardware.