Read only is a term usually used in the field of computers. The meaning of this term is fairly straight forward; it means simply that something may be accessed and read, but not changed in any way. This attribute can be voluntarily set with software only for the purpose of protecting one or more files. In some cases however, it can be a necessity. Optical disks are probably the best example of something which is read-only by necessity. CD-ROMs and DVDs which are not re-writable can only be written to once. After the data is recorded and the disk finalized, there is not way to add, change, or remove data.