A disk drive having a servo writer is disclosed. IR spectral information and chemical analysis of the samples is determined by using one or more IR sources, sampling accessories for positioning the samples, optically dispersive elements, a focal plane array arranged to detect the dispersed light beams, and a processor and display to control the FPA, and display an IR spectrograph. A dummy line is switched to the one of n bit lines by shifting from 1st bit line to the one of n bit line one by one according to the switching control signal for replacing the one of n bit lines. The extension rule may refer to a particular TCP flag. The method comprises measuring the charged voltage of a battery unit, determining the charging stage of the measured charged voltage, and sequentially and cyclically displaying icons that indicate a charging stage. The first character of the string corresponding to the current code is stored in the table location accessible by the next assignable code.