Documentation

In the executing sub-system of the client terminal, the error code can be stored, in the case of its occurring at an mql4 program execution. There is a specific last_error variable provided for every executable mql4 program. Before the init function is run, the last_error variable has been zeroized. If an error occurs during the process of calculation or that of calling the built-in function, the last_error variable takes the corresponding error code. Value stored in this variable can be got using the GetLastError function. At that, the last_error variable will be zeroized.

There is a number of critical errors that cause immediate stopping of program execution:

If the program stopped working due to a critical error, the code of this error can be read at the next launching of the start or deinit function using the GetLastError() function. The last_error variable is not zeroized before the start or deinit function starts.

There is a number of critical errors referred to imported functions call that cause immediate stopping of expert advisor or custom indicator execution the start function will not be launched until expert or indicator is re-initialized.

Other errors do not interrupt program execution.

The ERR_NO_MQLERROR (4000) code is never generated.

There is a number of errors which are possible only as a result of software or hardware failure.If any errors described below occur repeatedly, one should contact the developers.

There are some functions that always change the last_error variable value.

Some functions change value of the last_error variable only if an error occurs.

Other functions never change the last_error variable value.
AccountBalance, AccountCompany, AccountCredit, AccountCurrency, AccountEquity, AccountFreeMargin, AccountLeverage, AccountMargin, AccountName, AccountNumber, AccountProfit, AccountServer, Alert, CharToStr, Comment, Day, DayOfWeek, DayOfYear, DoubleToStr, GetTickCount, HideTestIndicators, Hour, IndicatorCounted, IsConnected, IsDemo, IsDllsAllowed, IsExpertEnabled, IsLibrariesAllowed, IsOptimization, IsStopped, IsTesting, IsTradeAllowed, IsTradeContextBusy, IsVisualMode, MathAbs, MathArctan, MathCeil, MathCos, MathExp, MathFloor, MathLog, MathMax, MathMin, MathPow, MathRand, MathRound, MathSin, MathSrand, MathTan, Minute, Month, NormalizeDouble, ObjectsDeleteAll, ObjectsTotal, OrderSelect, OrdersHistoryTotal, Period, Print, RefreshRates, Seconds, SetLevelStyle, StringConcatenate, StrToTime, StrToDouble, Symbol, TerminalCompany, TerminalName, TerminalPath, TimeCurrent, TimeDay, TimeDayOfWeek, TimeDayOfYear, TimeHour, TimeLocal, TimeMinute, TimeMonth, TimeSeconds, TimeToStr, TimeYear, UninitializeReason, WindowBarsPerChart, WindowFirstVisibleBar, WindowPriceOnDropped, WindowRedraw, WindowTimeOnDropped, WindowsTotal, WindowOnDropped, WindowXOnDropped, WindowYOnDropped, Year