Where does a program start at?

This is live notes from a talk about how programs are executed

Different programming projects have programs that start execution in different places. Let us look at some common examples.

• Javascript - starts from the top of the file. The file to run is usually specified in package.json.
• Python - starts from the top of the file. The file to run is mostly specified from command line. (Eg: python setup.py)
• R - starts from the top of the file. In R studio, we can run any line we want. (Python notebooks are similar)
• Java - “main” method of whichever class we specify. Depends.
• Modern web projects - index.html, script tags within html, package.json, build scripts
• Android - AndroidManifest.xml, lifecycle methods.

The biggest difference is between Object-Oriented languages like Java and scripting languages like javascript and python. They run programs in completely different ways.