[hyperman1]

I know of 1 smaller Cobol company. They alone had 10 to 100 million lines, after a decennium of trying to move to Java. Source files containing 1 routine were easily a few KLoc. The number in the article is probably too low.

The main problem with these code bases are they predate modern coding practices, so the sheer size, incomprehensability and untestability will crush you. You can easily spend your whole carreer reading the source code and reach pension age before you finish. Also, the organisational difference between 2 code bases is much bigger than modern code bases, as every company invented their own practices, and people rarely switched companies so didn't know what others were doing.