RTL is the Investor/RT Language, a formula language for composing trading signals, custom indicators, and scans. RTL is an end user language, designed to be used by those with little or no programming skills. RTL is used to write a formula. A formula may be a true/false condition, e.g. CLOSE < MA, that determines whether some condition is true or not for each bar (a signal) or the last bar (a scan). A formula may compute an arithmetic result, called a custom indicator. For example: MA ( HIGH - CLOSE ) computes a moving average of how far an instrument closes from its high. As you can see, RTL is more expressive, simpler, and easier to use than other market data languagues.