doubt in auto search

hey guys i want to know how exactly auto search feature works in our fm radios. without manually tuning how could it automatically changes frequency .

Are you asking about "scanning" to find stations? Since the local oscillator is a voltage-controlled oscillator (VCO) driven by a digital frequency synthesizer phase-locked loop (PLL), it is simple to step through all of the preassigned channels sequentially (simple digital counter). When the receiver lands on a channel with a signal on it, the signal is demodulated, and is used to stop the scan. The logic for this is implemented in a micro-controller which manages the memories and frequency display, too.

On CDs, MP3s and FM radio my car radio shows who sings or which group plays and shows the name of the song.
Of course it also scans radio stations.