Examples of ancient software still being used

The success rate of startups varies greatly depending on the industry or "idea pool." I am interested in forgotten industries where there is little to no software being used in various processes, or where ancient pieces of software are still being utilized.

Can you think of any ancient software that is still actively being used or purchased in niche industries? Ideally, this software is not tied to specific hardware, making it more accessible for outsiders to develop.