MetaTrader Program files have the EX4 extension. This is compiled programming code for MetaTrader, which is a free forex trading program. Scripts and indicators are stored in EX4 format for the MetaTrader software. A MetaTrader Custom Indicator file is used to compile EX4 programming code. For this, MetaEditor, the pre-installed application that comes with MetaTrader, is used.

Ex4 file or Ex5 file is created when the MQL4 or MQL5 file is compiled in the MetaTrader 4 or MetaTrader 5 platform, this is the simplest answer :)

An ex4 file is an executable program. These programs are also known as binaries. Exe4 files are compiled on the fly, meaning they are not written in source code. It will either be opened by another program or it can be executed directly by Windows using the command "run" or "double-click". The content of these files varies depending on what program it is for and how the user executes them.