1) I've started my programming career by creating new user interface for device that measures properties of metal joins on [BIG] machines [1]. It is used by many mining and energy companies. First version of this device was created somewhere in 70s so I guess this new one will last for many decades to come.
2) There was a time when every company created its own ERP software and I was hired to help maintain 500k lines of code monster that is used by fair chunk of construction companies in Austria. All the accounting, warehouse, quoting, payroll and what not was based on top of old Paradox database. Custom hacks were deployed to make sure we fit everything into 64kb of index space and I've got massive headaches trying to make work decades old database in networking mode. Another fun year was at the time when Vista changed memory layout and you sometimes crash everything because of memory location that was meant to be for printers is now occupied by sound stuff and you've touched protected memory. Anyway as far as I know this system is up and running, counting numbers, printing invoices, work orders and quotes all days long.
[1] https://www.popsci.com/resizer/meUXbu78Po3bGHtIFIaRTwBsLqg=/...