All programs require both input and output. A program that does not require input or output has no data to process, and without data to operate upon a program is essentially useless.
There can be good reasons not use certain input or output devices. For instance, a router has no need for a keyboard for input or a screen for output. However a router is network-enabled and the network interfaces are used for both input and output.
both input r output
I believe it is both an input and an output device, but I will check
"Touch screen "acts as both input and output devices
input
A USB port is both an input and an output.
It is both an Input and an Output device.
Normally it is an output device. However a touchscreen monitor is both an input and output device.
Since you can both read from (input) and write to (output) a hard disk, it is considered both an input and an output device.
INPUT
the magnatic disk is both as input and output media
both
A modem (Modulator-demodulator) is both. It allows you to input data (download) and output data (upload).