History of MQL5.community development

The article describes an example of creating a class for working with the trade server return codes and all the errors that occur during the MQL-program run. Read the article, and you will learn how to work with classes and objects in MQL5. At the same time, this is a convenient tool for handling errors; and you can further change this tool according to your specific needs.

By creating a sample program of visual design, we demonstrate how to design and construct classes in MQL5. The article is written for beginner programmers, who are working on MT5 applications. We propose a simple and easy grasping technology for creating classes, without the need to deeply immerse into the theory of object-oriented programming.

The article covers the problem of development of active control panels in MQL5. Interface elements are managed by the event handling mechanism. Besides, the option of a flexible setup of control elements properties is available. The active control panel allows working with positions, as well setting, modifying and deleting market and pending orders.

Working with data has become the main task for modern software - both for standalone and network applications. To solve this problem a specialized software were created. These are Database Management Systems (DBMS), that can structure, systematize and organize data for their computer storage and processing. As for trading, the most of analysts don't use databases in their work. But there are tasks, where such a solution would have to be handy. This article provides an example of indicators, that can save and load data from databases both with client-server and file-server architectures.

This article is a quick guide to MQL4 language functions, it will help you to migrate your programs from MQL4 to MQL5. For each MQL4 function (except trading functions) the description and MQL5 implementation are presented, it allows you to reduce the conversion time significantly. For convenience, the MQL4 functions are divided into groups, similar to MQL4 Reference.