does small embedded systems need an OS to run

Question

if i want to use an arduino to run a small program, do i need to install a whole OS inside arduino before being able to upload the code to the arduino?

and if i build my own microprocessor do i need to inject only the ide on the cpu to run a program or the whole os is needed?

Answer 1

Martin Taylor im a bit confused, what about driver softwares and other dependencies? will you have to add separate driver softwares on the microprocessor to be able to interact with the I/O. or should we implement our own functions for that? thx for replying