Others have mentioned hardware breakpoints but I also want to mention another type of breakpoint that can be used for both code and data and does not require pr

Others have mentioned hardware breakpoints but I also want to mention another type of breakpoint that can be used for both code and data and does not require program modification. And I can name at least one debugger that uses this method. The method is hooking Page Faults. Set the present flag of the page you want to debug to false and you'll be notified of any code that is executed there. But you can also be notified when data is accessed and by which instruction and address. On Windows this can be done with SEH and Linux has its own thing too.