Compiling

Compilation is the process of translating the source code of a MQL5 program into the machine language. This process consists of several stages:

• Lexical scan;
• Parsing;
• Semantic analysis;
• Code generation;
• Code optimization.

A successful compilation results in the creation of an executable file (*.EX5) of a program that can be started in the client terminal.

In order to start compilation, open the source file through the "Navigator" window and execute the " Compile" command in the "File" menu or in the "Standard" toolbar, or you can press the "F7" key.

The report of the compilation process will be shown in the "Errors" tab of the "Toolbox" window. If there are no errors in this tab, you can start the program in the client terminal. Error and warning messages are marked by special icons near their descriptions:

Compilation errors are marked by icons both in the "Errors" tab and in the code. If such errors occur, an executable program file (*.EX5) won't be generated. In order to move to the line with the error, click twice with the left mouse-button on the line, or execute the " Go to line" command in the context menu. The number of the line and column, where an error has been found, is shown in corresponding columns.

The appearance of alerts denoted by the icon point to places where errors can occur. I.e. the compiler points to parts of a source code, that could be incorrectly interpreted (for example, implicit change of a value type). You can go to such code lines the same as to lines with errors.

Besides, various informational messages are shown in the journal. They are marked by icons . They can show, for example, include files, to which a program referred during compilation.

Compilation from the Command Line

The client terminal includes the compiler of MQL5 programs that runs separately from MetaEditor — MQL5.exe. It is located in the terminal installation folder.

The compiler can be started from any folder. The only requirement for starting it is having MQL5.dll (or its 64-bit version) in the same directory.

The compiler is started from the command line, specifying the path and name of the file that you want to compile.

The file has two run keys:

• /s — If you run the compiler with this key, it will only check the program code syntax and shows respective results;
• /i :[path] — with this key, you can specify the path to the /MQL5 directory of the client terminal. This parameter is required, for programs that often use additional include files (*.mqh).