Somewhat inspired by an answer I gave about keyboard lights I now ask this: do computers actually need any sort of input (keyboard, mouse, touchpad, scanner, microphone, joystick, etcetera) or output (printer, display, speakers, etcetera)?
I recall an old axiom from C/C++ that states, roughly, that they don't expect any sort of input or output device being present in the machine (which is why, IMO, that there's no native and standard support for terminal interfaces).
But... what good is a computer if we can't get anything out of it? The whole point of computing was to feed data to a mechanism, that performed some actions, and then receive another set of data we could use.
A computer can, eventually, be left to it's own devices, but that way, we wouldn't get anything from it. I suppose a server rack could be considered a no input/output system, except that if it's a server, it communicates with a network so it does output something.
Some modern computers can't even work without a keyboard (I give the example of my own motherboard, that refuses to run without a keyboard).
I did try to search the Net for this, but most sites have only generalist tips or product recommendations. Either this question is as obvious as it is or it just hasn't been asked.
An update to the current status (essentially a sum-up of all things said):
The definition of input and output is crucial to the answering of this question. Assuming the broadest of terms (i.e. input as information coming in and output as information coming out) the following is true:
- Although a computer doesn't need any input or output, it would be useless without them.
- With this said, a computer may only need input and output for the time required to enter the commands/data and retrieve the processed data.
- A computer, internally, needs to pass information between it's components (CPU, RAM, HDD, etcetera) in order for it to function (thanks given to keltari for pointing this out).
Assuming more strict definitions of input and output (as being only those from HID, for instance), then computers may not need any such device (e.g. a server rack or a remote computer) in a direct form.