today’s digital devices use a variety of storage technologies. storage technologies, such as hard disks, store data as particles oriented north or south. a hard disk drive provides multiple for data storage that are sealed inside the drive case to prevent airborne contaminants from interfering with the read-write heads. hard disks are less durable than many other types of storage, so it is important to make a copy of the data they contain. storage technologies store data as a series of dark spots and light spots on the surface of cds and dvds. storage technologies, such as cd- , are used for distributing software and music, but you cannot alter the disc’s contents. technology allows you to write data on a cd or dvd, but you cannot delete or change that data. rerecordable or technology allows you to write and erase data on a cd or dvd. state storage technologies, such as usb flash drives, store data by activating electrons in a microscopic grid of circuitry. a backup is a copy of one or more files that have been made in case the original files become damaged. a good backup plan allows you to restore a device’s operating system, software, data files, settings, accounts, and profiles in case of a massive hardware failure or virus infection. personal computer backups are typically recorded on hard drives, usb flash drives, network servers, and online storage services. an easier way to get a backup of important data files is to use the command to make duplicates and store them on a usb drive. backup utilities such as file history and time machine use a technique called file to make sure that files on two devices are the same. a disk is a bit-for-bit copy of the data from all sectors of a hard disk.