A forward compatibility guaranteed data compression and decompression method and apparatus are provided. The light guiding member is in an approximately arc shape in a cross sectional view taken perpendicular to an optical axis. A bead is formed around a periphery of the image sensor. SDG is enhanced by expressing the symmetry present in the molecule, by making use of symmetry in the 2-D dynamics used to lay out rings and chains, by construction of bridges using an open polygon method together with a potential function, and by an elegant approach to the relative positioning of molecules. Therefore, a user can manipulate the apparatus without any inconvenience or accidental touches. While the electrical devices are each in a pre-boot environment, the management logic obtains information from the electrical devices and uses the information to determine electrical compatibility of, andor configure, the electrical devices.