External drives

Your computer has its own storage where files are saved. But external storage is also possible.

A simple example is a USB memory stick. When you connect it to your machine, the operating system mounts it and makes it available as a volume on the file system. The convenience of the memory stick is that it’s an easy way to transfer files from one machine to another (provided you have physical access to both).

Other devices may work the same way, including read-only devices like optical disks that read (and perhaps write) CDs and DVDs.

USB is not the only way to connect external storage devices to your computer. The Thunderbolt protocol, from Intel, is suitable for fast exchange of data and can connect physically using a USB, Lightning or DisplayPorts. (Incidentally, this is why DisplayPort is not always a video connection.)

Network-attached storage (NAS)

If your computer is connected to the local network (whether by Ethernet or WiFi) it’s also possible to access storage devices that are attached to that, instead of your computer.

These are often useful as backup devices. For example, you might configure your computer to copy its files onto the NAS overnight whenever it is connected to the network. The advantage of a NAS backup is that your backup is made conveniently and separately from the computer itself.

Note that NAS devices are not the same as storage in “the cloud”. That is external storage on the internet, not the local network (although there are ways to mount such remote stores so they appear to be local volumes).


Unlike built-in storage, remember that external devices can be disconnected too.

In general, it’s good practice to never disconnect a mounted drive suddenly. You should choose to eject it first, within the operating system. This gives your computer the opportunity to manage any open connections neatly, rather than them abruptly disappearing.