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What is firmware and how it works?
In electronics and computing, firmware is a term often used to denote the fixed, usually rather small, programs and data structures that internally control various electronic devices. Typical examples of devices containing firmware range from end-user products such as remote controls or calculators, through computer parts and devices like hard disks, keyboards, TFT screens or memory cards, all the way to scientific instrumentation and industrial robotics. Also more complex consumer devices, such as mobile phones, digital cameras, synthesizers, etc., contain firmware to enable the device's basic operation as well as implementing higher-level functions.
There are no strict boundaries between firmware and software, as both are quite loose descriptive terms. However, the term firmware was originally coined in order to contrast to higher level software which could be changed without replacing a hardware component, and firmware is typically involved with very basic low-level operations without which a device would be completely non-functional. Firmware is also a relative term, as most embedded devices contain firmware at more than one level. Subsystems such as CPUs, flash chips, communication controllers, LCD modules, and so on, have their own (usually fixed) program code and/or microcode, regarded as "part of the hardware" by the higher-level(s) firmware.
Simple firmware typically resides in ROM or OTP/PROM, while more complex firmware typically employs flash memory to allow for updates, at least in modern devices. Common reasons for updating firmware include fixing bugs or adding features to the device. Doing so usually involves loading a binary image file into the device, according to a specific procedure; this is sometimes intended to be done by the end user.
In some respects, the various firmware components are as important as the operating system in a working computer. However, unlike most modern operating systems, firmware rarely has a well-evolved automatic mechanism of updating itself to fix any functionality issues detected after shipping the unit.
Currently, one can fairly easily update the BIOS in a modern PC; devices like video cards or modems often rely on firmware dynamically loaded by a device driver and may thus get transparently updated through the operating system update mechanisms. In contrast, firmware in storage devices rarely gets updated, even when flash (rather than ROM) storage is used; there are no standardized mechanisms for detecting and updating firmware versions. However, in practice, such devices have a low rate of functionality issues compared to parts where the firmware may be updated. The reasons for this probably belong to the realm of psychology; a partial explanation could postulate that project managers may not invest the resources to error-proof code which that can be easily updated, as compared to when it "must be" correct in the very first production-run. A difference in complexity may be another factor, as devices with either fixed or "not easily updated" firmware tend to be simpler, and vice versa.
Most computer peripherals are themselves special-purpose computers. While external devices have firmware stored internally, as of 2010 modern graphics cards and peripheral expansion cards often have parts of the firmware loaded by the host system at start-up, as this provides greater flexibility. Such hardware may therefore fail to function fully until the host computer has "fed" it the requisite firmware, typically via a specific device driver (more exactly: via a start-up subsystem within a device driver package). Modern device drivers, whether for internal or external "peripheral" devices, may also expose a direct graphical user-interface for configuration, often using parts of a normal application program interface in addition to lower level operating system calls, hooks, and/or other interfaces designed for device drivers.
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