Block<\/th>	What it does<\/th><\/tr>\n <\/thead>\n
input<\/strong> parameters<\/td>\n	Settings you can change from the robot's dialog in MetaTrader 5, with no edit to the source: EMA periods, lot size, stop-loss, take-profit and the magic number.<\/td>\n <\/tr>\n
OnInit()<\/strong><\/td>\n	Runs once when the robot starts. Creates the two EMA handles and refuses to start if either one fails.<\/td>\n <\/tr>\n
OnTick()<\/strong>, new bar filter<\/td>\n	Runs on every incoming tick, then exits immediately unless a new bar has opened, so the strategy is evaluated once per candle.<\/td>\n <\/tr>\n
CopyBuffer()<\/strong> and the crossover test<\/td>\n	Reads the last three values of each EMA and compares the two closed bars to decide whether a crossover happened.<\/td>\n <\/tr>\n
CTrade<\/strong>, trade execution<\/td>\n	Sends the order, attaches the stop-loss and take-profit, and closes an opposite position first when the signal reverses.<\/td>\n <\/tr>\n
OnDeinit()<\/strong><\/td>\n	Runs once when the robot is removed from the chart and releases both indicator handles.<\/td>\n <\/tr>\n <\/tbody>\n <\/table>\n <\/div>\n\n Input Parameters<\/h3>\n\n The settings at the top of the file carry the `input<\/code> modifier, which exposes them in the robot's parameter window inside MetaTrader 5. In this example that covers the fast and slow EMA periods, InpFastEMA<\/code> and InpSlowEMA<\/code>, along with InpLotSize<\/code>, InpStopLoss<\/code>, InpTakeProfit<\/code> and InpMagic<\/code>.<\/p>\n\n` `The advantage is that changing a setting takes no edit to the source code. Values can be adjusted right before launching the robot, and the Strategy Tester can sweep through them during optimisation.<\/p>\n\n` <\/a>The Inputs tab exposes every parameter declared with the input modifier. Source: MetaTrader 5.<\/figcaption><\/figure>\n\n Initialization with OnInit()<\/h3>\n\n OnInit() runs once when the robot starts, which happens when you attach it to a chart or restart the terminal. It prepares the resources the robot needs later, creating the indicator handles that supply the EMA values.<\/p>\n\n When that preparation fails, the function returns INIT_FAILED<\/code> and the terminal stops the robot instead of running it half-configured. It also sets the magic number, the tag that marks every order this robot sends and lets it tell its own positions apart from anything else on the same symbol.<\/p>\n\n The Tick Event and the New Bar Filter<\/h3>\n\n OnTick() is the main function. The terminal calls it whenever a new tick arrives, meaning any change in the quote. Evaluating the strategy on every tick would be wasted work here, so a new bar filter cuts the processing down to once per candle.<\/p>\n\n The robot reads the opening time of the current bar with iTime()<\/code> and compares it with the time it processed last:<\/p>\n\n \n if(currentBarTime == lastBarTime)\n return;<\/code><\/pre>\n <\/div>\n\n When a new candle opens, that time changes and the robot continues. The strategy therefore reacts once per candle instead of following every price change inside it.<\/p>\n\n After the filter, the robot copies both EMAs with CopyBuffer()<\/code> and checks for a crossover. Index 1 holds the last closed bar and index 2 the bar before it, so the comparison never touches the candle still forming. EMA 9 crossing above EMA 21 raises buySignal<\/code>, crossing below raises sellSignal<\/code>, and only then does the execution block take over.<\/p>\n\n \n \n Where the robot sees a signal<\/div>\n Move the slider to advance the chart one bar at a time. The robot compares the last two closed bars, the same two values its code reads as index 1 and index 2.<\/div>\n\n \n \n EMA 9<\/span>\n EMA 21<\/span>\n Close price<\/span>\n <\/div>\n\n Bar on the chart<\/label>\n \n\n \n EMA 9, last closed bar<\/div>0<\/div><\/div>\n EMA 21, last closed bar<\/div>0<\/div><\/div>\n What the robot does<\/div>Waits<\/div><\/div>\n <\/div>\n\n No crossover on the last two closed bars, so the robot holds its position and waits for the next candle.<\/div>\n <\/div>\n\n

\n\n

The worked example uses a classic trend strategy: a crossover of two exponential moving averages, EMA 9 and EMA 21. The logic is simple enough to stay out of the way, which leaves room to understand the structure every expert advisor shares, from the file that MQL Wizard generates to the compiled robot placing its first test trade.<\/p>\n\n

The example uses a fixed 0.10 lot with a stop-loss and a take-profit attached to every position, and it evaluates signals<\/a> once per closed candle.<\/li>\n
A ready template gives you code you can read and verify. An AI chat is the better tool once you want to extend that code.<\/li>\n
Run it in the Strategy Tester first, then on a demo account, and check the Experts log before any live account is involved.<\/li>\n <\/ul>\n <\/div>\n\n
<\/span>The Working Environment: How to Open MetaEditor 5<\/span><\/h2>\n\n
Building a trading robot takes no third-party software. MetaTrader 5 already includes MetaEditor 5, the development environment for writing and editing MQL5 programs.<\/p>\n\n
MetaEditor combines the code editor, the compiler, the debugger, the MQL5 reference documentation and the built-in MQL Wizard, which generates ready-made templates for expert advisors, indicators<\/a> and scripts.<\/p>\n\n
Two ways to open it from the trading terminal:<\/p>\n\n
- Select Tools → MetaQuotes Language Editor<\/strong> from the top menu.<\/li>\n <\/ul>\n\n <\/span>Creating the Robot File with the MQL Wizard<\/span><\/h2>\n\n
  With MetaEditor open, the MQL Wizard builds the skeleton of the program for you. Start with File → New<\/strong>. The wizard offers a choice of program types, and the one for this example is Expert Advisor (template)<\/strong>.<\/p>\n\n
  $\"MQL$ <\/a>
  Step one of the MQL Wizard: choosing the program type. Source: MetaTrader 5.<\/figcaption><\/figure>\n\n
  Next comes the program description. The Name<\/strong> field takes the path and the file name, for example Experts\\MyFirstRobot<\/code>. Author<\/strong> and Link<\/strong> are optional and can stay empty.<\/p>\n\n
  <\/a>Step two: naming the expert advisor. Source: MetaTrader 5.<\/figcaption><\/figure>\n\n The wizard then offers extra event handlers, including OnTimer<\/strong> and OnTrade<\/strong>. This robot uses neither, so the defaults stay as they are.<\/p>\n\n <\/a>Step three: additional event handlers, left at their defaults. Source: MetaTrader 5.<\/figcaption><\/figure>\n\n The last screen covers the OnTester<\/strong> testing events. They are also unused here, so the parameters stay untouched and the wizard finishes.<\/p>\n\n <\/a>Step four: tester events, also left at their defaults. Source: MetaTrader 5.<\/figcaption><\/figure>\n\n MetaEditor now holds a new .mq5<\/code> file containing the basic structure of an expert advisor. That skeleton is the starting point for the trading logic.<\/p>\n\n <\/a>The generated template, with empty OnInit, OnDeinit and OnTick functions. Source: MetaTrader 5.<\/figcaption><\/figure>\n\n <\/span>The Ready-Made MQL5 Robot Code<\/span><\/h2>\n\n Below is the complete expert advisor built on the EMA 9 and EMA 21 crossover. Select everything in the generated template, delete it, and paste this in its place, so the .mq5<\/code> file holds only the robot code. After that it is ready to compile.<\/p>\n\n \n MyFirstRobot.mq5<\/div>\n \/\/+------------------------------------------------------------------+\n\/\/| MyFirstRobot.mq5 |\n\/\/| EMA 9 \/ EMA 21 crossover Expert Advisor |\n\/\/+------------------------------------------------------------------+\n#property copyright \"MyFirstRobot\"\n#property version \"1.00\"\n#property description \"Simple EMA 9\/21 crossover Expert Advisor\"\n\n#include <Trade\/Trade.mqh>\nCTrade trade;\n\n\/\/--- Trading parameters\ninput double InpLotSize = 0.10; \/\/ Lot size\ninput int InpFastEMA = 9; \/\/ Fast EMA period\ninput int InpSlowEMA = 21; \/\/ Slow EMA period\ninput int InpStopLoss = 200; \/\/ Stop Loss<\/a> in points\ninput int InpTakeProfit = 400; \/\/ Take Profit<\/a> in points\ninput ulong InpMagic = 123456; \/\/ Magic number\n\n\/\/--- Indicator handles\nint fastEMAHandle;\nint slowEMAHandle;\n\n\/\/--- Opening time of the last processed bar\ndatetime lastBarTime = 0;\n\n\/\/+------------------------------------------------------------------+\n\/\/| Expert initialization function |\n\/\/+------------------------------------------------------------------+\nint OnInit()\n{\n \/\/--- Create the Fast EMA indicator handle\n fastEMAHandle = iMA(_Symbol, _Period, InpFastEMA, 0, MODE_EMA, PRICE_CLOSE);\n\n \/\/--- Create the Slow EMA indicator handle\n slowEMAHandle = iMA(_Symbol, _Period, InpSlowEMA, 0, MODE_EMA, PRICE_CLOSE);\n\n \/\/--- Stop the robot if either handle failed\n if(fastEMAHandle == INVALID_HANDLE || slowEMAHandle == INVALID_HANDLE)\n {\n Print(\"Failed to create EMA indicators\");\n return(INIT_FAILED);\n }\n\n \/\/--- Tag every order<\/a>, so the robot only ever manages its own positions\n trade.SetExpertMagicNumber(InpMagic);\n\n Print(\"MyFirstRobot started successfully\");\n return(INIT_SUCCEEDED);\n}\n\n\/\/+------------------------------------------------------------------+\n\/\/| Expert tick function |\n\/\/+------------------------------------------------------------------+\nvoid OnTick()\n{\n \/\/--- Opening time of the current bar\n datetime currentBarTime = iTime(_Symbol, _Period, 0);\n\n \/\/--- Work once per bar, on the first tick after a new bar opens\n if(currentBarTime == lastBarTime)\n return;\n lastBarTime = currentBarTime;\n\n \/\/--- Dynamic arrays: the timeseries flag needs them\n double fastEMA[];\n double slowEMA[];\n\n \/\/--- Index 0 is the forming bar, 1 the last closed bar, 2 the one before it\n ArraySetAsSeries(fastEMA, true);\n ArraySetAsSeries(slowEMA, true);\n\n \/\/--- Copy the last three EMA values of each average\n if(CopyBuffer(fastEMAHandle, 0, 0, 3, fastEMA) < 3)\n return;\n if(CopyBuffer(slowEMAHandle, 0, 0, 3, slowEMA) < 3)\n return;\n\n \/\/--- Both checks read closed bars only, never the forming bar\n bool buySignal = fastEMA[2] <= slowEMA[2] && fastEMA[1] > slowEMA[1];\n bool sellSignal = fastEMA[2] >= slowEMA[2] && fastEMA[1] < slowEMA[1];\n\n \/\/+--------------------------------------------------------------+\n \/\/| Buy signal |\n \/\/+--------------------------------------------------------------+\n if(buySignal)\n {\n \/\/--- Look only at a position this robot opened itself\n if(PositionSelect(_Symbol) &&\n PositionGetInteger(POSITION_MAGIC) == (long)InpMagic)\n {\n long positionType = PositionGetInteger(POSITION_TYPE);\n\n \/\/--- A buy is already running, nothing to do\n if(positionType == POSITION_TYPE_BUY)\n return;\n\n \/\/--- Close the opposite position before reversing\n if(positionType == POSITION_TYPE_SELL)\n trade.PositionClose(_Symbol);\n }\n\n double ask = SymbolInfoDouble(_Symbol, SYMBOL_ASK);\n double sl = NormalizeDouble(ask - InpStopLoss * _Point, _Digits);\n double tp = NormalizeDouble(ask + InpTakeProfit * _Point, _Digits);\n\n trade.Buy(InpLotSize, _Symbol, 0, sl, tp, \"EMA 9\/21 Buy\");\n }\n\n \/\/+--------------------------------------------------------------+\n \/\/| Sell signal |\n \/\/+--------------------------------------------------------------+\n if(sellSignal)\n {\n if(PositionSelect(_Symbol) &&\n PositionGetInteger(POSITION_MAGIC) == (long)InpMagic)\n {\n long positionType = PositionGetInteger(POSITION_TYPE);\n\n if(positionType == POSITION_TYPE_SELL)\n return;\n\n if(positionType == POSITION_TYPE_BUY)\n trade.PositionClose(_Symbol);\n }\n\n double bid = SymbolInfoDouble(_Symbol, SYMBOL_BID);\n double sl = NormalizeDouble(bid + InpStopLoss * _Point, _Digits);\n double tp = NormalizeDouble(bid - InpTakeProfit * _Point, _Digits);\n\n trade.Sell(InpLotSize, _Symbol, 0, sl, tp, \"EMA 9\/21 Sell\");\n }\n}\n\n\/\/+------------------------------------------------------------------+\n\/\/| Expert deinitialization function |\n\/\/+------------------------------------------------------------------+\nvoid OnDeinit(const int reason)\n{\n \/\/--- Release the indicator handles\n if(fastEMAHandle != INVALID_HANDLE)\n IndicatorRelease(fastEMAHandle);\n if(slowEMAHandle != INVALID_HANDLE)\n IndicatorRelease(slowEMAHandle);\n}\n\/\/+------------------------------------------------------------------+<\/code><\/pre>\n <\/div>\n\n \n \n Test This Robot on a Free Demo Account<\/div>\n Full MetaTrader 5 access and real market conditions, with none of your own funds at stake.<\/div>\n <\/div>\n \n Open a Demo Account<\/a>\n <\/div>\n <\/div>\n\n <\/span>Code Anatomy: What Each Block Does<\/span><\/h2>\n\n The robot splits into five functional parts, each responsible for one stage of its work, from reading its settings to sending an order. Here is the map, followed by the detail on the parts worth understanding before you run it.<\/p>\n\n \n \n \n \n \n \n \n \n \n \n Block<\/th> What it does<\/th><\/tr>\n <\/thead>\n input<\/strong> parameters<\/td>\n Settings you can change from the robot's dialog in MetaTrader 5, with no edit to the source: EMA periods, lot size, stop-loss, take-profit and the magic number.<\/td>\n <\/tr>\n OnInit()<\/strong><\/td>\n Runs once when the robot starts. Creates the two EMA handles and refuses to start if either one fails.<\/td>\n <\/tr>\n OnTick()<\/strong>, new bar filter<\/td>\n Runs on every incoming tick, then exits immediately unless a new bar has opened, so the strategy is evaluated once per candle.<\/td>\n <\/tr>\n CopyBuffer()<\/strong> and the crossover test<\/td>\n Reads the last three values of each EMA and compares the two closed bars to decide whether a crossover happened.<\/td>\n <\/tr>\n CTrade<\/strong>, trade execution<\/td>\n Sends the order, attaches the stop-loss and take-profit, and closes an opposite position first when the signal reverses.<\/td>\n <\/tr>\n OnDeinit()<\/strong><\/td>\n Runs once when the robot is removed from the chart and releases both indicator handles.<\/td>\n <\/tr>\n <\/tbody>\n <\/table>\n <\/div>\n\n Input Parameters<\/h3>\n\n The settings at the top of the file carry the input<\/code> modifier, which exposes them in the robot's parameter window inside MetaTrader 5. In this example that covers the fast and slow EMA periods, InpFastEMA<\/code> and InpSlowEMA<\/code>, along with InpLotSize<\/code>, InpStopLoss<\/code>, InpTakeProfit<\/code> and InpMagic<\/code>.<\/p>\n\n The advantage is that changing a setting takes no edit to the source code. Values can be adjusted right before launching the robot, and the Strategy Tester can sweep through them during optimisation.<\/p>\n\n <\/a>The Inputs tab exposes every parameter declared with the input modifier. Source: MetaTrader 5.<\/figcaption><\/figure>\n\n Initialization with OnInit()<\/h3>\n\n OnInit() runs once when the robot starts, which happens when you attach it to a chart or restart the terminal. It prepares the resources the robot needs later, creating the indicator handles that supply the EMA values.<\/p>\n\n When that preparation fails, the function returns INIT_FAILED<\/code> and the terminal stops the robot instead of running it half-configured. It also sets the magic number, the tag that marks every order this robot sends and lets it tell its own positions apart from anything else on the same symbol.<\/p>\n\n The Tick Event and the New Bar Filter<\/h3>\n\n OnTick() is the main function. The terminal calls it whenever a new tick arrives, meaning any change in the quote. Evaluating the strategy on every tick would be wasted work here, so a new bar filter cuts the processing down to once per candle.<\/p>\n\n The robot reads the opening time of the current bar with iTime()<\/code> and compares it with the time it processed last:<\/p>\n\n \n if(currentBarTime == lastBarTime)\n return;<\/code><\/pre>\n <\/div>\n\n When a new candle opens, that time changes and the robot continues. The strategy therefore reacts once per candle instead of following every price change inside it.<\/p>\n\n After the filter, the robot copies both EMAs with CopyBuffer()<\/code> and checks for a crossover. Index 1 holds the last closed bar and index 2 the bar before it, so the comparison never touches the candle still forming. EMA 9 crossing above EMA 21 raises buySignal<\/code>, crossing below raises sellSignal<\/code>, and only then does the execution block take over.<\/p>\n\n \n \n Where the robot sees a signal<\/div>\n Move the slider to advance the chart one bar at a time. The robot compares the last two closed bars, the same two values its code reads as index 1 and index 2.<\/div>\n\n \n \n EMA 9<\/span>\n EMA 21<\/span>\n Close price<\/span>\n <\/div>\n\n Bar on the chart<\/label>\n \n\n \n EMA 9, last closed bar<\/div>0<\/div><\/div>\n EMA 21, last closed bar<\/div>0<\/div><\/div>\n What the robot does<\/div>Waits<\/div><\/div>\n <\/div>\n\n No crossover on the last two closed bars, so the robot holds its position and waits for the next candle.<\/div>\n <\/div>\n\n