Excuse my ignorance of such basic knowledge, but 3 books and several weeks of banging my head against my desk have driven me to this. I can't figure out how memory is mapped for the PICs (16c84). the data sheets show bank 0 from 00h to 7Fh and bank 1 from 80h to FFh. I think I've finally figured out the concept of data banks and register shadowing but their is a sample program in Predko's book that clears the STATUS flags as follows: movlw 0x0F8 andwf STATUS What does the "h" in the memory maps mean, and where does the final 8 in 0x0F8 fit in to this format. Also, 0x0F8 was never defined previously in the program. why was this address selected and how can you know what its value is. Another quick one: If a processor is rated at 4Mhz, why use only a 1Mhz crystal. thanks for your help.