It was one of the first languages (although not the first) that had a proper module system with separate compilation, implementation hiding, module nesting, and

It was one of the first languages (although not the first) that had a proper module system with separate compilation, implementation hiding, module nesting, and qualified exports / imports. It stops short of adding features like parameterized modules that confer significant problems for both theory and implementation. In typical Wirth fashion it was also quite minimal; you could write a complete Modula-2 compiler as a series of undergrad assignments. Here's a tutorial: http://www.modula2.org/tutor/chapter12.php http://www.modula2.org/tutor/chapter12.php It's kind of sad that proper module systems are not a part of more programming languages, but as the adage in the field goes, the languages most used to write modular software are the ones least suited to doing so.