Will the bootloader be erased if hex code is uploaded using programmer?

I am going to buy a programmer and test it out. Will the bootloader be erased if hex code is uploaded using programmer? If I want to use back the Arduino IDE, do I have to re-upload the Arduino bootloader back?

Right. If an Arduino ("chip", et al.) is uploaded via ICSP then the bootloader gets wiped out. To then upload to the Arduino via USB/serial will require its being re-bootloaded. You can upload via ICSP from within the Arduino IDE, too.

lightaiyee: I am going to buy a programmer and test it out. Will the bootloader be erased if hex code is uploaded using programmer?

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Yes.

lightaiyee: If I want to use back the Arduino IDE, do I have to re-upload the Arduino bootloader back?

Yes.

lightaiyee: I am going to buy a programmer and test it out. Will the bootloader be erased if hex code is uploaded using programmer? If I want to use back the Arduino IDE, do I have to re-upload the Arduino bootloader back?

Just make sure the last hex code file you program is a bootloader. :)