Externalstorage (also called auxillary storage) is any storage other thanmain memory. In modern times this is mostly hard drives and removeable media(such as floppy disks, Zip disks, optical media, etc.). With the advent of USBand FireWire hard drives, the line between permanent hard drives and removeablemedia is blurred. Other kinds of external storage include tape drives, drumdrives, paper tape, and punched cards. Random access or indexed access devices(such as hard drives, removeable media, and drum drives) provide an extensionof memory (although usually accessed through logical file systems). Sequentialaccess devices (such as tape drives, paper tape punch/readers, or dumbterminals) provide for off-line storage of large amounts of information (orback ups of data) and are often called I/O devices (for input/output).
