Is it possible for a program to open/close a circuit?

[scotty_le_b]

I just wondered if someone could programme a computer to, when certain data is inputted, open or close a circuit?

[martix]

The question is somewhat vague.
The computer by itself cannot do that. However you can program the computer to send the proper input/signal to an actuator or similar device that could physically accomplish the required task.
There are also lots of microcontoller packages on which you can load a program and install separately to accomplish the same task, which make it even easier since they provide a high level interface for a task which would otherwise involve a lot of low-level electrical engineering work.

[scotty_le_b]

Sorry about that I did mean by sending the signal.
Thanks :)