Quote Originally Posted by grimmjow View Post
i am just trying to understand the point of using other integrated circuits (like 18f2550) in pickit programmer. i was thinking "if we can write programs on other pics by using bootloader on 18f2550, why cant we do it by our computer? 18f2550 is just an interface on pickit programmer board and we can create this interface virtually on our computer."
There are some programmers that almost do this. They use the parallel port on the computer to program the chip. But it still needs a little hardware to bring the chip up to programming levels, etc.

Hopefully my bios example made some sense. Despite the chip having hardware, without code to set configure the chip, and code to tell the chip what to do with the hardware, nothing will happen.... Unless you have a programmer, like the pickit2 that puts a programming voltage to MCLR and send the bits into the chip using ICD programming port. Or load some software on the chip that sets up its hardware, and bootloader code that runs on the chip, letting it program its own code space.

And by the way, there are many older chips that do not allow programming their own code space, so these will never be able to use a bootloader, and you must program them with a programmer.

Walter