The modern day BIOS is one that has survived in essence for more than 25 years. However, the program and instructions themselves have been changed and adapted to match the ever quickening pace of technological advancement so much to be almost unrecognizable from its origins. The goals of the Extensible Firmware Interface (EFI), and now the Unified Extensible Firmware Interface (UEFI), is to eventually replace the aging BIOS, learning from both the mistakes and successes of the past 25 years. This paper provides an overview of the evolution of the EFI to the UEFI and from the Intel Framework specifications to the UEFI Platform Initialization (PI) specifications.