Nikon D5500 Reference Manual page 140

A
Flexible Program
In mode P, different combinations of shutter speed and aperture can
be selected by rotating the command dial ("flexible program"). Rotate
the dial right for large apertures (low f-numbers) and fast shutter
speeds, left for small apertures (high f-numbers) and slow shutter
speeds. All combinations produce the same exposure.
Rotate right to blur background details or
freeze motion.
Rotate left to increase depth of field or blur
motion.
While flexible program is in effect, a U (R)
indicator appears in the viewfinder and
information display. To restore default
shutter speed and aperture settings, rotate
the command dial until the indicator is no
longer displayed, choose another mode, or
turn the camera off.
116 P, S, A, and M Modes
Command dial