Good evening, not long ago MS-DOS came to mind; so thinking of Arduino the question of this forum came to my mind: is there a program for Arduino like DOS?
To go into details: is it possible to have an Arduino program that (using the SD card reading / writing shield) could be a terminal via serial connection?
Thank you very much for any information
Take a look at bitlash.net
I'll move this to Programming
is there a program for Arduino like DOS?
That would be an operating system.
I think the "big picture problem" is that there is no standard hardware interface for peripherals like a keyboard, display, or file storage. (And, it has limited memory.)
A bit more geeky than MSDOS: uLisp on Atmega
When you google for "atmega basic computer" you'll get more funny stuff, with and without keyboard/composite 
The attraction of the Arduino boards is that they DON'T have an operating system to get in the way of the sort of tasks that microprocessors are good at.
If you need a small footprint PC with an operating system consider using a Raspberry PI.
...R