From ideal to real switch. (I)

Inputs and outputs:

We can translate an outside action to a switch as an input - who modifies the projected image of the world to a particular electronic module.

Inputs act as translators of real world states to projected images (usually voltages and currents) inside electronic modules.

If the module itself act to a switch trying to change the outside world state we can refer to it as an output.

Outputs acts as actuators - the mechanism by which a control system acts upon an environment

Usually inputs tend to switch less power while outputs leverage high power. (changing the perception of the module vs. changing the world)

Electrical switching generated by a hand switch (input) or controlled relay or transistor (outputs) are not ideal.

Switching on and off either inputs or outputs are usual delayed in time more or less.

The transition in not immediate (inertia, propagation) and also most of the time asymmetrical the on/off (LO-to-HI) time can be less or more than off/on change.

Also in real world the switch transition (settling time) is affected by the material proprieties witch can have side effects like bounce (mechanical), oscillations (inductive & capacitive), rise time (charge) and fall times. Some of them can be attenuated, but some delay remains as trade-off. The delay is present to be assured that the switch has change state and is stable.

Operating time (switch on time / switch off time) will limit how fast we can switch. Usually semiconductor switches are faster then mechanical switches. 

Switch type, switch power capability and switch operating time will determine the switch that is used in an application.