Is there still a difference between a library and an API?

Question

Whenever I ask people about the difference between an API and a library, I get different opinions. Some give this kind of definition, saying that an API is a spec and a library is an implementation...

Some will tell you this type of definition, that an API is a bunch of mapped out functions, and a Library is just the distribution in compiled form.

All this makes me wonder, in a world of web code, frameworks and open-source, is there really a practical difference anymore? Could a library like jQuery or cURL crossover into the definition of an API?

Also, do frameworks cross over into this category at all? Is there part of Rails or Zend that could be more "API-like," or "libraryesque"?

Really looking forward to some enlightening thoughts :)

Answer 1

API is part of library that defines how it will interact with external code. Every library has API, API is sum of all public/exported stuff. Nowadays meaning of API is widened. we might call the way web site/service interact with code as API also. You can also tell that some device has API - the set of commands you can call.

Sometimes this terms can be mixed together. For example you have some server app (like TFS for example). It has API with it, and this API is implemented as a library. But this library is just a middle layer between you and not the one who executes your calls. But if library itself contains all action code then we can't say that this library is API.

Answer 2

My view is that when I speak of an API, it means only the parts that are exposed to the programmer. If I speak of a 'library' then I also mean everything that is working "under the hood", though part of the library nevertheless.