lights

make sure the redstone is behind your computer

print ("lights on or off")

input = read()

if input ==  "on" then
redstone.setOutput("back", true)
term.clear()
term.setCursorPos(1,1)

elseif input == "off" then
redstone.setOutput("back", false)
term.clear()
term.setCursorPos(1,1)

else

print ("Not a Valid Answer.")
sleep(3)
term.clear()
term.setCursorPos(1,1)

end

May I suggest you tell us what this does with out us having to read you code.

Also, remove the 'sleep(3)'. If you want to have a sleep in there, 1 second is the most you want.

I recommend putting a while loop around the entire thing so it will repeat it self, otherwise maybe add shell arguments.

A nice little tip to prevent repetition, you seem to have "term.clear() term.setCursorPos(1,1)" listed under all of the conditions. Why not just throw it after the if?

print ("lights on or off")

input = read()

if input ==  "on" then
redstone.setOutput("back", true)

elseif input == "off" then
redstone.setOutput("back", false)

else
print ("Not a Valid Answer.")
sleep(3)

end

term.clear()
term.setCursorPos(1,1)

Otherwise it's a nice, solid program for a beginner.