Introduction to USB keys

A USB key is a compact-format removable storage device which can be plugged into a computer's USB port.

A USB key is a plastic shell carrying a USB connector and flash memory, a solid-state, non-volatile, rewritable kind of memory; that is, it has many of the same characteristics as RAM, except that the data is not wiped out when the machine is turned off.

For this reason, a USB key can store up to several gigabytes of data, and keep the data saved when electrical power is cut off (i.e. when the key is unplugged).

In practice, a USB key is very practical for users who go from one computer to another, as it is very easy to transport and can store a large quantity of documents and data.

What's more, recent motherboards can boot from USB keys, which means that you can now start an operating system from a simple USB key! Very useful for users who want to carry their own work environment wherever they go, or for restarting and fixing a system after a crash.

Characteristics

The features to take into account when choosing a USB key are:

• Storage capacity
• Transfer rate: This is the speed at which data is transfered. It should be noted that the transfer rate when reading is different from the transfer rate when writing, as the process of writing to flash memory is slower. The transfer rate depends on the read speed and write speed of the Flash memory component, as well as the USB standard supported:
  • USB 1.1 (low-speed USB), which can reach 12 Mbit/s,
  • USB 2.0 (high-speed USB) which can reach 480 Mbit/s. It should be noted that in order to attain the full transfer speed, the key must be plugged into a USB 2.0 port. Otherwise (with a USB 1.1 port), the key will run at a low speed.
• Encryption features: Some keys have tools for encrypting data or some of the data found on the key, in order to strengthen privacy.
• Write protection: Some keys include a hardware switch for putting the key in read-only mode, to prevent data from being changed or erased.
• Multimedia functions: When a USB key includes a headphone jack and can play audio files (generally in the MP3 format), it is called an MP3 player.