Software developers have produced special versions of operating systems and common place applications that run from live USB Flash Drives. These systems are typically optimized for size and configured to place temporary or intermediate files in the computers main RAM rather than store them temporarily on the Flash Drive.
USB Flash Drives with this functionality are known as Live USBs. Live USBs are the successor to the Live CD; they have all the CDs functionality and more. They can be used in embedded systems administration, operating system testing, data recovery and for many other duties. Examples of operating systems that can be run from a USB Drive are: XP Windows embedded; SUSE, Ubuntu; Mepis; Fedora; Knoppix and Dyne: bolic.
Live USB are much faster than live CDs and have the benefit that they can also be written to, so data along with the operating system can be saved on the USB Flash Drive. Live USBs are obviously a lot easier to carry than laptops, more discreet and can also be locked away relatively easily in a safe. The absence of moving parts from USB Flash Drives leads to faster seek times than hard drives or optical media can achieve, this allows small programs to start faster than disk based media.
Although a seemingly brilliant idea, live USBs haven't really taken off. In 2005 Finger gear released the computer-on-a-stick flash drive that incorporated a whole operating system plus office suite within a 256mb USB Flash Drive, but that was clearly not an overwhelming success. Maybe the reason for this though was not the idea, but the capacity of the USB Flash Drives. Nowadays 4GB USB Flash Drives only cost £ 10 and installing a decent operating system onto one is easier than ever; it maybe that the computer on a flash drive idea goes through a renaissance this year. So watch out!