Computers and servers without general purpose operating systems?

Question

Programming

Out of curiosity: are bare computers with ugly GUIs or none at all being used for specific tasks? With their own OS in the minimum configuration, or even more - with direct access to hardware by a highly specialized program? Without layers in the form of Windows, Linux, Unix, other rare operating systems for solving common problems.
I mean full-fledged tasks: miscalculation of algorithms, physics, data analysis, graphics, etc.

Answer 1

I have such an idea, and there is a task.
The problem is that those pitiful extra percentages of productivity will be achieved with such titanic work that it is terrible to imagine.
In general, heavy task vendors usually prefer to buy a couple of hundred cores than to grind out software in pursuit of an extra percentage in the report.

Answer 2

Such devices are called embedded systems , if I understand you correctly.