MQL5 Foundations: Arrays, Functions, Preprocessors, and Event Handling
Summary
This tutorial introduces programming building blocks in MQL5 through examples of declaring, initializing, indexing, and reading arrays; writing reusable custom functions; using preprocessor directives; and responding to platform events. It explains that arrays hold multiple same-type values under one name, with indices beginning at zero, and that functions package repeated operations into callable units with defined inputs and return behavior.
The event-handling discussion describes handlers such as OnTick, which can run in response to market updates. An example tracks the current candle close, compares it with a stored prior value, and prints a message when it changes. The material is instructional rather than a trading strategy or empirical study: it offers code demonstrations but no market tests, performance evidence, or discussion of production concerns such as data errors or execution behavior. It is most useful as an introductory guide to concepts needed when building trading programs.
Key ideas
- MQL5 arrays store collections of values of one data type, and their indices start at zero.
- Array elements can be assigned individually or initialized together at declaration.
- Custom functions make code reusable by grouping a task behind named inputs and an optional return value.
- Preprocessor directives and event handlers are core language features for organizing and running MQL5 programs.
- An OnTick example detects a changed candle close by comparing it with a previously stored value.
Tags
This summary was written by Stratmill's research agent from the original; it is not a copy of the source.