Difference between an API and SDK

apisdk

I am trying to explain to a non-developer the difference between an API an SDK. I need to explain why a commercial fingerprint software vendor will likely not provide an SDK, although they may certainly have used one.

Both device vendors and software vendors can and should expose a well-defined API. This API allows other software programs to (be written to) inter-operate with the vendor’s own software components or hardware devices.

If someone has more ideas to explain this clearly, I would very much appreciate the suggestions. I want to emphasize that the goal is to explain the concepts to a non-programmer who does not know developer lingo.

Specifically, in the context of a fingerprint sensor versus software to do enrollment/verification, here is how I attempted to explain it:

If I am a fingerprint device/sensor manufacturer and not in the
business of writing software, the ways I could better market my
product are:

  1. Make sure my device drivers are installable on a wide variety of operating systems
  2. Define and provide an API for software developers to write programs (e.g., for enrollment, verification) to “talk” to or use my
    device
  3. Develop and provide an SDK (one step beyond an API) to make it easier and faster for software developers to write programs that work
    with my device. SDKs may provide helper code libraries, reference
    applications, documentation etc.

Best Answer

Piece of cake:

  • an API is an interface. It's like the specification of the telephone system or the electrical wiring in your house. Anything* can use it as long as it knows how to interface. You can even buy off-the-shelf software to use a particular API, just as you can buy off the shelf telephone equipment or devices that plug into the AC wiring in your house.
  • an SDK is implementation tooling. It's like a kit that allows** you to build something custom to hook up to the telephone system or electrical wiring.

*Anything can use an API. Some APIs have security provisions to require license keys, authentication, etc. which may prohibit complete use of the API in particular instances, but that's only because particular authentication/authorization steps fail. Any software that presents the right credentials (if required) can use the API.

**Technically, if an API is well-documented, you don't need an SDK to build your own software to use the API. But having an SDK generally makes the process much easier.

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