A Keil developer is primarily responsible for developing, testing, and debugging embedded system applications. They use Keil µVision, a window-based software development platform, to write code mostly for microcontrollers. The developer utilizes the platform's simulation capabilities to test the efficiency and functionality of their code. Keil developers also analyze and correct software errors, modify existing software for optimization, and integrate software with hardware components. They are expected to have a good understanding of embedded systems, C/C++ programming and hardware interfacing. Their work is crucial in the design and development of many electronic devices and systems.