This is example of the indicator, that shows bars index in the "Data Window".
The bar indexing is set as timeseries, it means that current uncompleted bar has index=0, the oldest bar has the highest index. Note that the indicator doesn't plot anything (DRAW_NONE), despite the fact that red color for the first graphic plot is defined.
See also: The Drawing Styles in MQL5.
Translated from Russian by MetaQuotes Software Corp.
Original code: https://www.mql5.com/ru/code/329
The Roulette Game.iChartsSwitchSymbol
When the chart symbol is changed, it will change symbols for all other charts.