The A and C inputs are internal parts of one of the analog blocks (which is nothing for the rookies to deal with).
I cannot tell much about your #define (yet) can you post a link to the original appnote?
Found it in AN58128. The line is:
INSAMP_OUT_TO_ADC ASC21CR1&=0x80; ASC21CR1|=0x9F
This macro generates two C-statements. The first is clearing bits 0 to 6 of the register anf the next is setting bits 0 to 4.
thank u ....but still i am confused with A & C inputs. theres something to do with it. which input is selected when we change the value of registers
thanks & regards