Use flag variable in the user's profile table of your database. When the user login to the system update the field with value 1 and update 0 when he/the log out from the system. Then display a green light icon if that field in database is 1 else show gray light icon wherever you required.
APLX is a very complete implementation of the APL programming language from MicroAPL. The company stopped producing it in 2016 and it has been taken over by Dyalog. While Dyalog ...