I worked at a bank that had a windows-based trading system and for some reason created folders to hold the details of each book. There were issues when a trader decided to call a book "LPT1".
I've spent the last 20 years of my career working for investment banks. Never seen a windows based trading system. Frankly picking windows as a target platform for trading infra is asking for trouble. Everyone seems to know that and build on top of Linux. When was that?
No, it's most often not related to any particular client. Rather the book is a list of all buy and sell orders that didn't match sitting there and waiting for someone to take the other side of the trade
