A program method of a nonvolatile memory device according to example embodiments includes a operation of detecting a level of a program voltage; and a operation of providing a unselected word line voltage and a bit line precharge voltage having a variable level respectively according to the detected level of the program voltage. The light-transmitting optical system includes a light-shield mask having a translucent portion to define a beam profile of the measuring light. R8 and R9 are independently \u2014H or \u2014CH2-Sec. Armrests are mounted to a front surface of the back support and may be selectively pivoted into front surface channels.