As of the year 2010 more than 70% of the stock shares traded on the [[New York Stock Exchange|NYSE]] and [[NASDAQ]] are generated from [[automated trading system]]s. {{Citation needed|date=July 2011}}
[[Automated trading]] systems are computer [[software program]]s designed to trade stocks, [[futures]] and [[Foreign exchange market|forex]] based on a predefined set of rules which determine when to enter a trade, when to exit it and how much to invest in it.
[[Algorithmic trading|Trading system]] designers / programmers often test their automated trading systems on historical or current [[market data]] in order to determine whether the underlying [[algorithm]] guiding the system is profitable or not.
Backtesting software are special [[trading platform]]s which enable trading system designer to develop and test their trading systems
on historical market data while aiming to produce optimal historical results.
