One might sensibly ask why I'm posting it if it has all these limitations? The rationale here is that I want individuals of all levels to realise that building algorithmic trading systems is hard work and requires a lot of attention to detail! There is a significant amount of scope for introducing bugs and incorrect behaviour. I want to outline how "real world" systems are built and show you how to test for these errors and correct them.
Margins are a hotly debated topic. Some traders argue that too much margin is very dangerous, however it all depends on trading style and the amount of trading experience one has. If you are going to trade on a margin account, it is important that you know what your broker's policies are on margin accounts, and that you fully understand and are comfortable with the risks involved. Be careful to avoid a Forex margin call. 

A Portfolio Margin account can provide lower margin requirements than a Margin account. However, for a portfolio with concentrated risk, the requirements under Portfolio Margin may be greater than those under Margin, as the true economic risk behind the portfolio may not be adequately accounted for under the static Reg T calculations used for Margin accounts. Customers can compare their current Reg T margin requirements for their portfolio with those current projected under Portfolio Margin rules by clicking the Try PM button from the Account Window in Trader Workstation (demo or customer account).
When investors are selling, the exchange rate of the foreign currency tells them how many units of the quote currency they will get for one unit of the base currency. Traders make decisions to buy if they think that the value of the base currency might increase. In the example, traders would purchase the US dollar with the Euro if they expect the value of the US dollar to increase to $1.31. The change that takes place is how the investor makes a profit.