ADC alignment

I am trying to know what is real use of ADC alignment ? wheather right alignment or left alignment

I have tried searching on google..failed to get satisfactory answer for it
what will be the effect for 12-bit ADC cortex m4 core if I put
1.right alignment or
2.left alignment


Thanks,
Kie

The use is simply how you want to handle the data - the classic example would be to left justify it and read just the top byte to get an 8 bit result. Personally I'd normally right justify it if I was wanting full resolution, but the option is there is you prefer it left justified.

Left alignment can be used for Q formatted data. It's used a lot in DSP applications to avoid floating point arithmetic in hardware without floating point support.