Travin77, You need to look in the data sheets for the PIC micro you are using. For instance in the data sheet for the 16F88 bits 7 & 6 of ADCON0 register need to be set to binary equiv. of 3 for the internal RC clock source for the A/D. This is the same as the DEFINE ADC_CLOCK 3 statement.

Dave Purola,
N8NTA