____ is a specialized kind of portable software used to operate in-built computers

The term you are looking for is "Firmware."

Firmware is a specialized kind of portable software that is used to operate the built-in computers within various devices. It is embedded into the hardware and provides low-level control for the device's specific functions. Unlike regular software applications that can be easily modified and updated, firmware is often stored in non-volatile memory and is designed to function closely with the hardware to perform essential tasks. Examples of devices that use firmware include smartphones, televisions, cameras, and other electronic gadgets. Firmware updates can enhance performance, fix bugs, or add new features, but they tend to be more challenging to implement compared to standard software updates due to their close integration with the hardware.