FIX-3-3.5 is a version of the Financial Information Exchange (FIX) protocol. It is one of the oldest FIX versions, released in 1996, and is one of the most widely deployed versions of the FIX protocol. It has been used for many years to exchange data related to trading operations. FIX-3-3.5 is used for pre-trade, execution, and post-trade messages, and supports messages for order entry, modification, cancellation, and status inquiries. It also supports market data, stock market pricing, risk management, and analytics messages. FIX-3-3.5 is a relatively old version of FIX, and is now being phased out.