a process may block on a call to an I/O device

[Daljeet12]

I am trying to understand meaning of following statement shown in page https://en.wikipedia.org/wiki/Process_state

For example, a process may block on a call to an I/O device or Processes also commonly block when they require user input

I/O stand for input/ output device. can anyone give at least three real stuation to get idea

 

[betwixt]

simple example:
Your program prints "press enter to continue". Until you press the key your program doesn't continue, it is 'blocked'.

In electronic terms, it means your program is held up waiting for a signal from somewhere else before it can continue. For example, it might be in a loop waiting for a switch to close or an I/O pin to go to a logic high.

With careful programming it is possible in most cases to code in a non-blocking way so other processes can continue while still waiting for the input to change.

Brian.