Supercomputers
Supercomputers are a class of very powerful computers that have extremely fast processors, as of 2008, they are capable of performing several hundred Tflops, i.e. 1012 floating point operations per second (Oxford, 2008).
Large main-memory capacity and large numbers of microprocessors working in parallel are the other main characteristics. They are used in meteorology, engineering, astronomy and nuclear physics and there at present, several hundred are in operation worldwide.

and the fastest is...
The fastest supercomputer in the world as of November 2012 is the Titan Cray XK7, performing at a record of 17.59 petaflops per second – that's quadrillions of calculations per second!
Titan has AMD Opteron CPUs in conjunction with Nvidia Tesla GPUs to maintain energy efficiency while providing an exponential increase in computational power over Jaguar its predecessor.
Titan Cray XK7 Specification
- It uses 18,688 CPUs, paired with an equal number of GPUs
- Performs at 17.59 petaFLOPS
- Theoretical peak of 27 petaFLOPS
- Has 560,640 cores
- 710,144 GB of memory
- Requires 8,209.00 kW of power
- And finally, uses the an adapted version of the Linux OS called the Cray Linux Environment
Figures taken from (Oakridge, 2013). To give you a rough idea of just how powerful this machine is, 20 petaFLOPS is more than 20,000 trillion, floating point calculations per second.
Built by Cray at Oak Ridge National Laboratory for use in a variety of science projects, the Titan is an upgrade of Jaguar, which uses both graphics processing units (GPUs) in addition to conventional central processing units (CPUs), and is the first such hybrid to perform at over 10 petaFLOPS. The upgrade began in October 2011, commenced stability testing in October 2012 and it will be available to researchers in early 2013. The initial cost of the upgrade was US$60 million, funded primarily by the United States Department of Energy (Top 500 List, 2012).