What is the lengthiest program you know till date?

Question

I have recently read that ISS is being operated and is programmed with 10 million lines of code.

Answer 1

IIRC Google and similar services use billions of lines of code to operate.

Answer 2

There is a picture explaining how many lines of code some software uses https://informationisbeautiful.net/visualizations/million-lines-of-code/