Getting Started with MEX

Introduction to MEX scripting

So you’ve got a board running. Callers are logging in, messages are flowing, files are moving. Everything works. But now you want to make it yours — a custom welcome screen that knows who’s calling, a trivia game for the regulars, a voting booth, maybe something nobody’s ever seen on a BBS before.

That’s what MEX is for.

What Is MEX?

MEX — the Maximus Extension Language — is a real programming language built right into your board. It looks a lot like C, feels a lot like BASIC in spirit, and runs inside the Maximus VM so your callers experience it live, in real time, right at their terminal.

MEX isn’t a toy. It has variables, functions, loops, string handling, file I/O, direct access to the user record and message base, lightbar menus, and even HTTP networking. Parts of the standard Maximus distribution are written in MEX — the file and message area headers, pieces of the Change Menu, and more.

But it’s also not scary. If you can edit a TOML file, you can write MEX. The compiler catches your mistakes before callers ever see them, and the worst thing a buggy script can do is print something weird.

What You’ll Need

A text editor — anything that saves plain ASCII. Your system editor, nano, vim, VS Code, whatever you like.
The MEX compiler (mex) — ships with Maximus. It reads your .mex source files and compiles them into .vm bytecode that the board can run.
A running board — so you can test your scripts with a real caller session (even if that caller is you, logged in from another terminal).

The Three-Step Path

This section covers the essentials — just enough to get something running:

MEX Compiler — What the compiler does, how to invoke it, and what the output looks like.
Script Structure — The anatomy of a .mex file: includes, functions, main(), and how it all fits together.
Hello World — Write it, compile it, wire it to a menu option, and watch it run.

After that, you’ll know enough to be dangerous. Which is exactly where Learning MEX picks up — a hands-on, lesson-by-lesson journey from “hello” to a working mini-game on your board.

Where Things Live

MEX source files (.mex) and compiled bytecode (.vm) typically live in your Maximus m/ directory. Header files (.mh) — especially the all-important max.mh — live there too.

To run a compiled MEX script from a menu, you add a MEX command option pointing to the .vm file. That’s it. One menu entry, one script, one happy caller. (Details are in the Menu Options reference under the MEX command.)

Ready?

Pick up at the MEX Compiler if you want the methodical walk-through, or jump straight to Learning MEX if you learn by doing and want the fun version.

Maximus BBS