Adding a sign in button is simply:
This allows the user to log in and grant permission for your app to access LinkedIn.
Anders Hejlsberg - Compiler Construction The Modern Way
What you are taught as the theory of compiler construction in computer science is simply out of date. See what Anders Hejlsberg has to say on theory versus practice.
Google's Science Journal Android App For Experiments
We need to find good ways for young people to get started with real science and data. Google has produced an Android app that just might help - it sounds fun too.