Often it is needed to see what exactly is happening inside your micro while your code is getting executed. You can use a simulator to test run your program and can see what exactly will happen with the registers when your run it on your target micro. If you want to see the register content while code is getting executed in the micro you can either send them through the UART to PC serial port and on PC you can use a terminal program such as hyperterminal, TeraTerm etc to see these values. You can also see the register contents by other methods such as putting them onto an LCD screen etc. if you have one connected to your system. I usually use LCD method when I want to do the same.

Regards,
Prahlad Purohit