The predefined Variables

For each executable mql5-program a set of predefined variables is supported, which reflect the state of the current price chart by the moment a mql5-program (Expert Advisor, script or custom indicator) is started.

Values of predefined variables are set by the client terminal before a mql5-program is started. Predefined variables are constant and cannot be changed from a mql5-program. As exception, there is a special variable _LastError, which can be reset to 0 by the ResetLastError function.




The _AppliedTo variable allows finding out the type of data, used for indicator calculation


Number of decimal places


Size of the current symbol point in the quote currency


The last error code


Timeframe of the current chart


Current status of the generator of pseudo-random integers


Program stop flag


Symbol name of the current chart


Uninitialization reason code


The _IsX64 variable allows finding out the bit version of the terminal, in which an MQL5 application is running

Predefined variables cannot be defined in a library. A library uses such variables that are defined in program from which this library is called.