how to start a program using a redstone signal

How do i start a program using a redstone signal?
for example: there is a redstone wire on the back side of the computer, and i want a program to run when that wire is on, how do i do that?

you can use the redstone api

e.g.

while not rs.getInput("back") do
  os.pullEvent("redstone") --redstone even sends an event
end
shell.run("hello")