Default visibility. Other components can reference the symbol, and the symbol definition can be overridden (preempted) by a definition of the same name in another component.

Protected visibility. The symbol is treated as though it is defined in another component. It also means that the symbol can be overridden by a definition of the same name in another component.

Hidden visiblity. Other components cannot directly reference the symbol. However, its address may be passed to other components indirectly.

Protected visibility. The symbol cannot be referenced outside its defining component, either directly or indirectly.

Protected visibility. Other components can reference the symbol, but it cannot be overridden by a definition of the same name in another component.