Display device having non-volatile display unit driven with power supplied from battery

A method of controlling a nonvolatile display unit by using electric power supplied from a battery, the nonvolatile display unit being configured so as to be capable of displaying an image and maintaining the displayed image even when the nonvolatile display unit is supplied with no electric power, the method comprising:

• receiving an image rewrite instruction to perform an image rewriting operation to change an image currently displayed in the nonvolatile display unit;
• determining an amount of power that remains in the battery;
• and
• controlling, in response to the image rewrite instruction, the nonvolatile display unit to perform an image rewriting operation to change the currently-displayed image if the amount of power that remains in the battery is greater than or equal to a threshold value and controlling the nonvolatile display unit not to perform the image rewriting operation if the amount of power that remains in the battery is smaller than the threshold value.

A computer readable storage medium storing a set of program instructions for controlling a nonvolatile display unit by using electric power supplied from a battery, the nonvolatile display unit being configured so as to be capable of displaying an image and maintaining the displayed image even when the nonvolatile display unit is supplied with no electric power, the instructions comprising:

• receiving an image rewrite instruction to perform an image rewriting operation to change an image currently displayed in the nonvolatile display unit;
• determining an amount of power that remains in the battery;
• and
• controlling, in response to the image rewriting instruction, the nonvolatile display unit to perform an image rewriting operation to change the currently-displayed image if the amount of power that remains in the battery is greater than or equal to a threshold value and controlling the nonvolatile display unit not to perform the image rewriting operation if the amount of power that remains in the battery is smaller than the threshold value.