determining if an application is open

Hello, once again I will state that I am a beginner to Applescripting.

I am trying to figure out how to create the following

if
BBEdit is not open
launch BBEdit

if it is open
continue with rest of script

You shouldn’t need to check if it’s running. If it’s already running, the launch won’t have any effect.

tell application "BBEdit" to launch
-- the rest of the script