Acientsoft

Acientsoft was a company made in 1 Vigintillion BTE (0E1e+308-1 Vingintillion) and ended in 1 Million BTE (0E1e+308-1000000) succeeded by Oggosoft

Wrong Theories about Oggosoft being 1st company to make OSES
It is not actually Oggosoft or Acientsoft

This was discovered in 2421 when a french guy named Jacqués De Marçou time traveled to 1 Vigintillion BTE (0E1e+308-1 Vingintillion) and found a man [or FAR (First Ancestral Race) from Neon Genesis Evangelion], (Its name is unknown) who had a PC developer and a sign that said:"WE ARE ACIENTSOFT, AND WE WILL BE THE FIRST COMPANY TO MAKE THE FIRST OPERATING SYSTEM EVER EXISTED IN OUR PROTO-UNIVERSE! OUR RIVAL, CAMONISE INC. IS FIGHTING AGAINST US TO BE THE FIRST COMPANY TO MAKE OS. WE SHALL RACE AGAINST THEM TO DECIDE WHO WILL BE FIRST!  SUPPORT US!  DON'T TRUST CAMONISE!  GOOD THINGS COME FROM US!"And another sign says:"OUR FIRST OS, ACIENTDOWS 1.0, IS COMING SOON BY 2 MONTHS!"

Rumored Competitors
Camonise Inc. (very ancient Apple Inc.-like company founded the same year Acientsoft was created) (succeeded by Oppo Co.)

Nadar (very ancient Linux-like company)