Firmware can be found on any electronic devices such as mobile phone, computer hardware and measurement instrumentation. Basically the downloading codes to the Read Only Memory (ROM) are called flashing. The size of the ROM really depends on the complexity of the hardware and the microcode itself. Thus, the firmware incorporates the microcontroller, operating systems for user interface and data storage as well. Firmware is a matter of software and the internal algorithm written specifically for the targeted device and stored in the internal volatile or non-volatile Flash ROM such as the Intel Bootblock based technology, which can be found at large. The firmware codes contain the microcontroller instruction and the user interface that acts like operating systems to perform some special function on those particular devices. The firmware upgrade circuit has been designed and implemented for a mobile phone.
Firmware is the heart of many electronic devices.
It stores and performs multiple functions according to the program code written on it. Each modern electronic device is the most often made with a special microprocessor, memory, input and output devices, some power source, internal software, which manage everything and some other. Mobile phones are the same. They contains own special made microprocessors, keyboard and loudspeaker for entering data, displays, speaker, buzzer for giving data to user, battery and software, which manage it and other parts for sending and receiving data to and from network.
Software, which manages everything, is called firmware.
When user change or modify it, the user can change partially functionality of the device. Often firmware is written specially for one device model and cannot be used for other because they have different hardware. But not always it is the rule, sometimes its better, cheaper and easier to make family of similar phones...