i want to know the use of boot-loader file. need your favor.
Bootloader is the first program which executes before the main program whenever a system is initialized. It make the micro-controller as a self programmable device using UART.
By using boot loader you could eliminate programmer to program the device.
The bootloader can be inserted into a controller by using an external or any conventional burner and then depending on the type of bootloader the controller starts responding to the interface. whenever the controller is reinitialized the program counter jumps to the bootloader section and then it waits there for the instruction, which is fed from external device. In case there is no bootloader the program counter will go on 0000H (starting position of the flash memory) and start executing the instructions which are written in the memory of the device.