MQL5, or MetaQuotes Language 5, is a high-level programming language designed for creating trading robots, technical indicators, scripts, and libraries in the MetaTrader 5 (MT5) platform. It is based on C++ and provides robust features to automate trading strategies, analyze financial data, and manage trading operations effectively.

This tutorial covers the foundational concepts of MQL5, including its syntax, structure, and essential programming elements. It is intended for those looking to develop trading applications or automate strategies within the MT5 environment. By the end of this guide, you will have the necessary knowledge to start creating your own Expert Advisors (EAs) and scripts.

What Is MQL5?

MQL5 is a specialized programming language developed by MetaQuotes Software for creating trading applications in MT5. It is tailored for creating tools that enhance trading experience, including:

  • Expert Advisors: Fully automated trading systems.
  • Indicators: Visual tools for analyzing market conditions.
  • Scripts: Used to automate repetitive or specific trading actions.
  • Libraries: Reusable sets of functions to simplify development.

Key features of MQL5 include:

  • Event-driven programming: Actions are executed in response to predefined events, such as market tick updates or timer triggers.
  • Wide range of functions: MQL5 provides built-in functions for analyzing quotes, handling positions, and managing trade requests.
  • Debugging tools: A built-in debugger and profiler make it easier to refine your code.

MQL5 builds upon its predecessor, MQL4, but introduces more robust and object-oriented capabilities, making it better suited for complex and high-performance trading systems.

Why Choose MQL5?

MQL5 offers several advantages for algorithmic trading enthusiasts:

  • Speed: Its low-level access to trade execution ensures fast operations.
  • Flexibility: Developers can use advanced data structures, functions, and object-oriented programming (OOP)
  • Community Support:  A vast community of traders and developers provides extensive libraries, tutorials, and forums.
  • Integration: Full compatibility with MetaTrader 5 allows seamless backtesting and optimization.

Understanding the MQL5 Development Environment

To begin coding in MQL5, you will use the MetaEditor. This integrated development environment (IDE) comes bundled with MetaTrader 5 platform and offers:

  • SyntaxHighlighting: Makes reading and debugging code easier.
  • Code Completion: Speeds up the development process.
  • Debugger: Helps identify and resolve issues efficiently.
  • Strategy Tester Integration: Simplifies backtesting and optimization.

MQL5 File Types

When working with MQL5, you’ll encounter different file types, each serves a specific purpose:

  • .mql5: Source code files.
  • .ex5: Compiled executable files used by MetaTrader 5. This is the one that is executed/run in the MT5 chats.
  • .mqh: Header files for reusable code snippets.

Setting Up Your Environment

To start programming in MQL5, you need the MetaTrader 5 platform installed on your computer. Here are the steps to set up your environment:

  1. Download MetaTrader 5: Visit the official MetaTrader website and download the platform.
  2. Install MetaEditor: MetaEditor is the integrated development environment (IDE) for MQL5. It comes bundled with MT5.
  3. Access MetaEditor: Open MetaTrader 5 and navigate to File > Open MetaEditor. This will launch the IDE where you’ll write and test your MQL5 programs.

Understanding the MQL5 Program Structure

An MQL5 program typically consists of several predefined functions. Here are the main components:

1. Header Section

The header section includes important definitions and includes files needed for your program. For example:

#include <Trade/Trade.mqh>  // Include the trade library

2. OnInit() Function

This function runs when your program is first initialized. It’s used to set up initial variables or configurations.

int OnInit() {
    Print("Program Initialized");
    return(INIT_SUCCEEDED);
}

3. OnTick() Function

For Expert Advisors, this function executes on every market tick. It’s where most of your trading logic resides.

void OnTick() {
    double price = SymbolInfoDouble(_Symbol, SYMBOL_BID);
    Print("Current Price: ", price);
}

4. OnDeinit() Function

This function runs when your program is deinitialized, allowing you to clean up resources.

void OnDeinit(const int reason) {
    Print("Program Deinitialized");
}

5. Other Event-Handling Functions

  • OnTimer(): Fires at regular intervals if a timer is set.
  • OnTrade(): Captures trading-related events.

Basic Syntax and Data Types

MQL5 shares many similarities with C++, so if you’re familiar with it, you’ll find the learning curve manageable. Here are some basics to get you started:

Variables and Data Types

MQL5 supports several data types:

  • int: Integer values (e.g., int x = 10;)
  • double: Decimal values (e.g., double price = 1.2345;)
  • string: Text values (e.g., string name = "Trader";)
  • bool: Boolean values (true or false)

Operators

Common operators include:

  • Arithmetic: +, -, *, /, %
  • Comparison: ==, !=, <, >, <=, >=
  • Logical: &&, ||, !

Conditional Statements

Use if, else if, and else for decision-making:

if (price > 1.5) {
    Print("Price is high");
} else {
    Print("Price is normal");
}

Loops

MQL5 supports for, while, and do-while loops. For example:

for (int i = 0; i < 10; i++) {
    Print("Count: ", i);
}

Creating Your First Expert Advisor

Let’s create a simple EA that prints the current bid price of a currency pair for every tick.

Step 1: Create a New EA

  1. Open MetaEditor.
  2. Go to File > New > Expert Advisor (template).
  3. Follow the wizard to name your EA and generate the boilerplate code.

Step 2: Add Code to OnTick

Replace the OnTick function with the following:

void OnTick() {
    double bid_price = SymbolInfoDouble(_Symbol, SYMBOL_BID);
    Print("Current Bid Price: ", bid_price);
}

Step 3: Compile and Test

  1. Click the Compile button or press F7 to check for errors.
  2. If successful, return to MetaTrader 5.
  3. Attach your EA to a chart to see it in action.

Core Components of MQL5

1. Object-Oriented Programming

MQL5 embraces OOP, unlike it’s predecessor MQL4, allowing developers to use:

  • Classes: Define objects and methods.
  • Inheritance: Extend existing classes for reusability.
  • Polymorphism: Implement dynamic method behavior.

2. Functions

Functions encapsulate reusable logic and can accept parameters or return values.

3. Error Handling

Error handling is critical for robust trading systems. MQL5 provides the GetLastError() function to retrieve the last runtime error. Common error codes are detailed in the MQL5 documentation.

Debugging and Testing

Built-in Debugger

The MetaEditor debugger helps identify logical errors in your code. Use breakpoints and step-through execution to analyze your program’s behavior.

Strategy Tester

The Strategy Tester in MT5 allows you to backtest your EA using historical data. Go to View > Strategy Tester, select your EA, and run tests to evaluate its performance.

Best Practices

  1. Start Simple: Focus on understanding the basics before attempting complex strategies.
  2. Use Comments: Add comments to explain your code, making it easier to understand and maintain.
  3. Test Thoroughly: Always backtest and optimize your EA in the Strategy Tester before using it in live trading.
  4. Stay Updated: Explore the MQL5 documentation for advanced features and best practices.

Conclusion

Learning MQL5 opens up endless possibilities for automated trading. With its powerful features and integration with MT5, you can transform your trading ideas into reality. This tutorial introduced you to the basics of MQL5, from setting up your environment to creating a simple Expert Advisor. With practice and exploration, you’ll be well on your way to mastering this language and unlocking the full potential of algorithmic trading.

For more in-depth tutorials and advanced examples, keep an eye on the upcoming content at this blog or subscribe to the Savanna Techie YouTube Channel. Start experimenting today, and let the journey to automated trading begin!

As always,  Stay curious, stay lazy (in the right way), and keep coding.

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