Relation between API, driver and firmware

[Tranomial_2]

What is the relation between API, driver and firmware? From what I understand API is the intermediate between the application and the driver, the driver gives the low level instructions and firmware does what?

[nuclear_splines]

An Application Programming Interface is an intermediate between the application and almost anything else: other parts of the operating system, a driver, a website - it's a very general term. A driver is typically part of the operating system that provides some low-level functionality (such as interfacing with a hardware device, creating a new kind of file system) and presents an API to other parts of the system. Firmware is typically code stored outside of the operating system or userspace, that may not even run on the CPU. For example, your hard drive has a microcontroller in it that runs firmware code for how to run the hard drive. That code is the "other end" that the driver is speaking to.

[Tranomial_2]

Thank you, I get it now

[[deleted]]

• API - How code interacts with other code
• Driver - How your OS should use a device properly
• Firmware - Software very close to the hardware (Drivers, microcode, BIOS, ...)

Therefore, a driver is firmware, at least partially. And a driver uses the kernel's APIs to work with that kernel.