so the advantage is an easy way to update firmware in products, or an easy
way to develop software and reprogram without ISP....
cool...


> Actually, a bootloader is a piece of code which resides on the PIC, and is
the
> first thing that runs when turned on.  Upon boot-up of the PIC it checks a
pin
> and based on whether the pin is high or low, it goes into a special
programming
> mode where you can program the rest of the PIC through the UART, or it
runs the
> program already stored.  This eliminates the need for a programmer or
ICSP(in
> circuit serial programming) or could be considered a form of ICSP.  No
high
> (+13.5) programming voltages are needed.
>
> This has really only come up now (in the world of PICs) with the
widespread use
> of the flash chips 16f8xx which can write to their own program flash.
>
> Bootloaders were (and are) widely used on other architechtures where the
program
> and data memory are not seperate (8051, 68k, etc).  The ROM of such a
device
> might have the bootloader, which loads a program from a serial port into
the
> memory, and then starts program operation at that point in memory.  This
isn't
> something new to the world, only to the PIC line of uControllers.
>
> -Adam