I am working with alsa and I had the next problem:
I get a signal from the mic and then put it in a file. The harware parameters are:

Interleaved mode
SND_PCM_FORMAT_U8 - 8 unsigned bits
speed = 5500 Hz
1 channel - Mono

I want to calculate the FFT on the file's values.
But how I can understand this kind of file? What does it mean all of this simbols ?
I know a few about DSP - PCM and ADC but i can not understand this kind of values.
What is the relationship between adquire sound from the mic (8 bit 1 channel 5500 Hz) and the info's file?
The idea is turn this kinf of value to another like int, or binary numbers.

Thanks.

Ulises.