Principally used for backup of important files from the hard disk and for the long term storage and archiving of data.
they are small, robust, portable and provide low cost storage per GB
they are very slow to write to and read from
serial access means all the data on the tape must be read before you can access the data you need
External hard disks
An external hard disk can store very large amounts of data, eg 1TB, and can be plugged into your computer via a USB or FireWire port to provide extra storage. They're essentially the same as the hard disk in your computer but due to the casing are usable externally.
high capacity, eg 1TB or more so they can be used to backup data or move large amounts of data between machines
they are often quite large and therefore inconvenient to carry around
they have moving parts so are more likely to break, especially if dropped
A memory stick is a 'pen top' sized USB device and can be used in a similar way to a floppy disk but it is inserted into the USB port - it is then seen by the computer as a removable drive. They typically come in sizes from 512MB to 32 GB upwards depending on the price paid.
memory sticks can hold large quantities of data
they are extremely portable, so the user can take them wherever they go
they are durable, because they have no moving parts
portable storage devices in general are more likely to be lost, stolen or damaged
A memory card is a stamp-sized USB device and can be used in a similar way to a floppy disk but it is inserted into either a memory card reader or a USB converter - it is then seen by the computer as a removable drive. They typically come in sizes from 1 GB to 32 GB upwards, depending on the price paid. There are many available memory card formats, but since 2010 the SD card became the more favoured format.
memory cards can hold large quantities of data
they are extremely portable so the user can take them wherever they go
digital accessories such as compact cameras and mobile phones are able to read and write to memory cards allowing the user to transport large collections of photographs, songs or information with them
they are durable because they have no moving parts
Memory cards, specifically the micro SD card, are the smallest storage devices available. This means they are more likely to be lost, stolen or damaged.
All computers do not come with memory card readers built in. Users will often be required to purchase a card reader or USB converter to view the data on a card.