Ryan Pogge wrote:
>
> what is a "bootloader"?

A machine (controlled by a pic, of course) which automatically loads boots from
the factory to a truck for all the cowboy boots sold in the summer months.
You're hearing more about them now on the pic list because all the boot
manufacturers are gearing up for this summer's boot production.  "Wear the
official boot of the millenium!"  etc, etc.

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