portOutputRegister() ??

what are these functions for :

portOutputRegister() digitalPinToPort() digitalPinToBitMask() portModeRegister()

I found these inside a class for driving an OLED from Sparkfun

Each of the digital I/O pins on the Arduino is a member of a group of pins called a port. Each port has several 8-bit registers that control the behavior of up to 8 pins. To manipulate an Arduino pin you need to know which port it is associated with and which of the eight bits within the port controls that particular pin. Those functions get that information from a set of data tables specific to each Arduino model.