From LTwiki-Wiki for LTspice

MSEE, PE, 35+ yrs experience Design Engineer Rad-hard, consumer electronics, medical, sensors ICs, PCBs I have worked at fortune 500 companies, startups, and medium sized companies. I first used SPICE with punch cards on IBM mainframe. After that, I moved to Mentor Graphics SPICE, then LTSPICE. It is so much easier now, but it is the same "under the hood".