What exactly is the purpose of a bootloader?

 

Take a look at the definition provided by wikipedia for the term bootloader.

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From Wikipedia:

Early programmable computers had a row of toggle switches on the front panel to allow the operator to manually enter the binary boot instructions into memory before transferring control to the CPU. The boot loader would then read the operating system in from an outside storage medium such as paper tape, punched card, or a disk drive.

Gee, I thought the bootloader was the operator, who would flip the switches to enter the boot instructions, make a mistake, and kick (boot) the machine in frustration!

--Rich

 

It's a variation on a common theme of pulling yourself up by your own bootstraps. The purpose is to get a large program into the code space and begin executing it.

Many chips come preprogrammed with SPI, serial, or USB bootloaders.

 

The Atmel AT89C5131 has a factory-installed bootloader on the chip. You can get a little understanding of the function of the bootloader from its datasheet.

Basically it is a program that runs when you boot up the chip. This program waits for communication with a USB Host (PC) for the purpose of downloading your own code (which you hv compiled and linked) into the chip.