MQL4/MQL5

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  1. MQL4/MQL5: A Comprehensive Guide for Beginners

This article provides a detailed introduction to MQL4 and MQL5, the programming languages used for developing trading robots (Expert Advisors), custom indicators, scripts, and libraries for the MetaTrader 4 and MetaTrader 5 platforms, respectively. It’s geared towards beginners with little to no prior programming experience.

Introduction to MetaTrader and Algorithmic Trading

MetaTrader 4 and MetaTrader 5 are the world’s most popular electronic trading platforms, widely used for trading Forex, CFDs, and Futures. They offer a user-friendly interface for manual trading, but their real power lies in their ability to support algorithmic trading. Algorithmic trading, also known as automated trading, involves using computer programs to execute trades based on predefined sets of instructions. These programs, developed using MQL4 or MQL5, can analyze market data, identify trading opportunities, and automatically place and manage trades without human intervention.

Why use algorithmic trading? Several reasons:

  • **Elimination of Emotional Bias:** Trading robots execute trades objectively, free from fear, greed, or other emotions that can cloud human judgment.
  • **Backtesting:** MQL4/MQL5 programs can be backtested against historical data to evaluate their performance and optimize their parameters. This is vital for risk management.
  • **24/7 Trading:** Robots can trade around the clock, even when you're asleep or unavailable.
  • **Speed and Efficiency:** Automated systems can react to market changes much faster than humans.
  • **Diversification:** You can run multiple trading strategies concurrently.

Understanding MQL4 and MQL5

MQL stands for MetaQuotes Language. MQL4 is the language used for MetaTrader 4, and MQL5 is the language used for MetaTrader 5. While they share similarities, they are *not* fully compatible. MQL5 is a more powerful and advanced language, offering improvements in speed, functionality, and optimization.

Here’s a breakdown of the key differences:

| Feature | MQL4 | MQL5 | |------------------|------------------------------------------|-----------------------------------------| | Platform | MetaTrader 4 | MetaTrader 5 | | Data Types | Limited | Expanded (e.g., datetime, string) | | Optimization | Slower | Faster and more efficient | | Strategy Tester | Simpler | More sophisticated, multi-currency backtesting | | Object Orientation| Limited | Full object-oriented programming support | | Event Handling | Less flexible | More flexible and robust | | Testing Accounts | Only one strategy tester at a time | Multiple strategy testers simultaneously | | Market Depth | Not available | Available |

Despite these differences, the core concepts of programming in both languages are similar. Learning MQL4 can provide a good foundation for learning MQL5 later.

Core Components of MQL4/MQL5 Programs

MQL4/MQL5 programs come in four main types:

  • **Expert Advisors (EAs):** These are automated trading systems that can open, close, and manage trades. They are the most complex type of MQL program. An EA might employ a moving average crossover strategy.
  • **Custom Indicators:** These are tools that analyze price data and display it visually on a chart. Examples include Fibonacci retracements, Bollinger Bands, and Relative Strength Index (RSI).
  • **Scripts:** These are one-time execution programs that perform specific tasks, such as closing all open orders or modifying stop-loss levels.
  • **Libraries:** These are collections of functions that can be reused in multiple programs. They promote code modularity and reusability.

All MQL4/MQL5 programs are built around a set of predefined functions and variables provided by the MetaTrader platform. These functions allow programs to access market data, manage orders, and interact with the trading environment.

Basic Programming Concepts

Before diving into MQL4/MQL5 code, let's cover some essential programming concepts:

  • **Variables:** Variables are used to store data. They have a name and a data type (e.g., integer, double, string, boolean). Example: `int orderTicket;`
  • **Data Types:**
   * `int`: Integer numbers (whole numbers)
   * `double`: Floating-point numbers (numbers with decimal places) - used for prices and calculations.
   * `string`: Text strings.
   * `bool`: Boolean values (true or false).
   * `datetime`: Represents date and time.
  • **Operators:** Operators are symbols that perform operations on variables and values (e.g., +, -, *, /, =, >, <, ==).
  • **Functions:** Functions are blocks of code that perform specific tasks. They can accept input parameters and return values. Example: `double iMA(string symbol, int timeframe, int period, int ma_method, int shift, double applied_price);` This function calculates the moving average.
  • **Conditional Statements:** Conditional statements (e.g., `if`, `else if`, `else`) allow programs to execute different code blocks based on certain conditions.
  • **Loops:** Loops (e.g., `for`, `while`, `do-while`) allow programs to repeat a block of code multiple times.
  • **Arrays:** Arrays are used to store collections of data of the same type.

A Simple MQL4/MQL5 Example: Printing "Hello, World!"

Let’s look at a very basic example to illustrate the structure of an MQL4/MQL5 program. This program simply prints "Hello, World!" to the Experts tab in the MetaTrader terminal.

    • MQL4:**

```mql4 //+------------------------------------------------------------------+ //| HelloWorld.mq4 | //+------------------------------------------------------------------+

  1. property copyright "Your Copyright Here"
  2. property link "Your Link Here"
  3. property version "1.00"

int OnInit() 

 {
  Print("Hello, World!");
  return(INIT_SUCCEEDED);
 }

//+------------------------------------------------------------------+ ```

    • MQL5:**

```mql5 //+------------------------------------------------------------------+ //| HelloWorld.mq5 | //+------------------------------------------------------------------+

  1. property copyright "Your Copyright Here"
  2. property link "Your Link Here"
  3. property version "1.00"

void OnInitialize() 

 {
  Print("Hello, World!");
 }

//+------------------------------------------------------------------+ ```

Key differences to note:

  • **`OnInit()` vs. `OnInitialize()`:** The initialization function has a different name in MQL5.
  • **Return Value:** `OnInit()` in MQL4 returns an initialization status code, while `OnInitialize()` in MQL5 is void (doesn’t return a value).

Developing an Expert Advisor: A Simplified Example

Let's create a very simplified EA that opens a buy order if the current price is below a specified level. This is *not* a profitable strategy, but it illustrates the basic structure of an EA.

    • MQL5 (Simplified Buy EA):**

```mql5

  1. property copyright "Your Copyright Here"
  2. property link "Your Link Here"
  3. property version "1.00"

input double BuyLevel = 1.1000; // Input parameter for the buy level

void OnTick() 

 {
  double Ask = SymbolInfoDouble(_Symbol, SYMBOL_ASK);

  if(Ask < BuyLevel)
    {
     // Open a buy order
     MqlTradeRequest request;
     MqlTradeResult  result;

     ZeroMemory(request);
     ZeroMemory(result);

     request.action   = TRADE_ACTION_DEAL;
     request.symbol   = _Symbol;
     request.volume   = 0.01; // Lot size
     request.type     = ORDER_TYPE_BUY;
     request.price    = Ask;
     request.sl       = Ask - 50 * _Point; // Stop loss (50 pips)
     request.tp       = Ask + 100 * _Point; // Take profit (100 pips)
     request.deviation= 20;

     OrderSend(request, result);

     if(result.retcode != TRADE_RETCODE_DONE)
       {
        Print("OrderSend failed: ", result.retcode);
       }
    }
 }

//+------------------------------------------------------------------+ ```

    • Explanation:**
  • **`input double BuyLevel = 1.1000;`**: This declares an input parameter that allows you to set the buy level from the EA's settings.
  • **`OnTick()`**: This function is called on every tick (price change).
  • **`SymbolInfoDouble(_Symbol, SYMBOL_ASK);`**: Gets the current ask price.
  • **`if(Ask < BuyLevel)`**: Checks if the ask price is below the buy level.
  • **`MqlTradeRequest` and `MqlTradeResult`**: These structures are used to define the trade request and receive the result.
  • **`OrderSend(request, result);`**: Sends the trade request to the MetaTrader server.
  • **Error Handling**: The `if(result.retcode != TRADE_RETCODE_DONE)` block checks for errors during order execution.

This is a very basic example. A real-world EA would be much more complex and would likely incorporate advanced technical indicators, price action analysis, and money management techniques.

Resources for Learning MQL4/MQL5

  • **Official MetaQuotes Documentation:** [1](https://www.mql5.com/en/docs)
  • **MQL5 Community:** [2](https://www.mql5.com/en) – A vast forum with tutorials, code examples, and expert advice.
  • **ForexFactory:** [3](https://www.forexfactory.com/) – A popular forum for Forex traders, with a dedicated MQL section.
  • **Babypips:** [4](https://www.babypips.com/) – A comprehensive Forex education website.
  • **YouTube:** Search for "MQL4 tutorial" or "MQL5 tutorial" to find numerous video tutorials.
  • **Books:** "Expert Advisor Programming for MetaTrader 4" by Andrew R. Young and "MetaTrader 5 Programming" by Vladimir Nikulin.

Important Considerations

  • **Risk Management:** Always implement robust risk management techniques in your trading programs. Use stop-loss orders, take-profit orders, and appropriate lot sizing. Understand the concepts of drawdown and risk-reward ratio.
  • **Backtesting and Optimization:** Thoroughly backtest your programs against historical data to evaluate their performance and optimize their parameters. Be aware of the dangers of curve fitting.
  • **Debugging:** Learning to debug your code is crucial. Use the MetaEditor debugger to identify and fix errors.
  • **Market Conditions:** Trading strategies that work well in one market condition may not work well in another. Consider adapting your strategies to changing market dynamics.
  • **Broker Regulations:** Be aware of the regulations governing algorithmic trading with your broker. Some brokers may have restrictions on the use of EAs.
  • **Continuous Learning:** The Forex market is constantly evolving. Stay up-to-date on the latest trading strategies, technical indicators, and market trends. Explore concepts like Elliott Wave Theory and Ichimoku Cloud.



MetaTrader 4 MetaTrader 5 Expert Advisor Technical Analysis Forex Trading Backtesting Risk Management Moving Average Fibonacci Retracement Bollinger Bands Relative Strength Index (RSI) Stop Loss Take Profit Lot Size Curve Fitting Drawdown Risk-Reward Ratio Elliott Wave Theory Ichimoku Cloud Price Action Candlestick Patterns Support and Resistance Trend Lines MACD Stochastic Oscillator Average True Range (ATR) Commodity Channel Index (CCI) Parabolic SAR Donchian Channels Heikin Ashi

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