Building a guitar tuner.. need some help!

How do most guitar tuners determine the frequency of the incoming signal? Thanks

ans to ur question

when the string of the giutar is toughen up.. then sunsunidal waves increases as and when the frequency increases

Dunno, but it'd be based on a frequency to voltage chip(commonplace), going into an ADC(analogue to digital converter) , then the digital output would go into a 'binary word- to - musical note' encoder (you'll need to make that yourself) , going into 7-segment display driver for the output.