Your First MQL Script: Reading the Chart

MQL (MetaQuotes Language) is the C-like language that powers MetaTrader bots. You don't need to be a programmer to start — you need to understand three ideas: events, series, and functions. We'll use all three in a few lines.

Events: code that runs when something happens#

An MQL program hooks into events the platform fires. The most important is OnTick() — called every time the price updates:

// Runs once when the program starts
void OnInit()
{
   Print("Script started on ", _Symbol);
}

// Runs on every new price tick
void OnTick()
{
   double price = SymbolInfoDouble(_Symbol, SYMBOL_BID);
   Print("Current bid: ", price);
}

Load that onto a chart and it prints the live price on every tick. That's a working MQL program — no magic.

Series: price is an array#

Historical prices are arrays indexed from the most recent bar backwards. Close[0] is the current bar, Close[1] the one before, and so on. Indicators work the same way.

Putting it together: a moving-average signal#

void OnTick()
{
   // 20-period and 50-period moving averages on the current symbol
   double fast = iMA(_Symbol, PERIOD_CURRENT, 20, 0, MODE_EMA, PRICE_CLOSE, 0);
   double slow = iMA(_Symbol, PERIOD_CURRENT, 50, 0, MODE_EMA, PRICE_CLOSE, 0);

   if (fast > slow)
      Print("Uptrend: fast EMA above slow EMA");
   else
      Print("Downtrend: fast EMA below slow EMA");
}

This is the heartbeat of a trend-following bot. Swap the Print calls for order commands and you have an Expert Advisor — but never do that before you've backtested the logic.

What you just learned#

• Code runs in response to events (OnInit, OnTick).
• Price and indicators are series you index from the current bar back.
• Built-in functions like iMA() do the heavy lifting.

From here, every trading bot is just more rules stacked on these same bones. For more, browse the MetaTrader articles and our latest writing.