Already so many discussions about grounding. But the more I read, the more I got confuse as there are many disputes. The above are cases where grounding are quite confusing. Grounding or earthing, I consider are same. There stacked lines, three parallel diagonal lines, and a triangle pointing down I consider are same function even they are referring to specific purpose. In this case the picture 1 also is not valid using them. But for now, we may forget it.
The first schematic is showing a simple circuit with grounding. The second picture also a simple circuit schematic without grounding. As you can see, both are designed by two professors from two high class universities.
The third and the fourth picture are schematic of a boost converter I designed in an online electronic software design here, which the source voltage is 5V DC output of USB or 5V DC Power Bank, and expected the output voltage will be around 12V DC. The third picture shows one warning 1 bad connection, but it works. The fourth circuit shows no warning (except telling that no resistor to the grounding line) but the circuit doesn't work. It only loop between the capacitor and the 1k ohm resistor. If I add resistor between the circuit and the grounding sign, then circuit works exactly as what is in the picture three, without grounding, and also show the same error, 1 bad connection.
Then my question, what is the canonical (valid) rule to put grounding in schematic? And what is that grounding for? As I knew, sometimes grounding place in a schematic is due to the complexity of the schematic which is not easy to connect them to a common line which will finally connect to the neutral (0V) of the source.