I've seen many tutorials on programming a ATmega 328 via Arduino. If i'm right, the atmega need to be bootloaded. I thought to remove the atmega present on the arduino board. But to bootloading atmega we need another atmega on the arduino board. I can't buy a new one. After bootloading we need only one IC. So, can I remove the atmega which is present on the arduino and directly program it? Can I consider it as a bootloaded one?
Arduino controllers are usually already bootloaded with Arduino. So yeah, you can use the chip on the arduino. Or you can buy a programmer to bootloaded empty chips.
In Arduino board, arduino controller means ATMEGA328P-PU already bootloaded. So, you can use directly. But if you buy only ATMEGA328P-PU chip or any other ATMEGA chip then you have to do bootloading for that.
Arduino boards come with the bootloader already installed. You only need to flash a bootloader to it if something damaged the original one. When you buy replacement chips, you generally have a choice of "factory fresh" ones (no bootloader) or ones that already have a bootloader installed, at a small difference in price.