Untangling API vs. Library vs. Framework

A framework will help you run your code and provides an environment for programmers to build inside. Frameworks determine the order things occur inside of the program. To contrast, a library is used by the code and says when/how to use code. An application programming interface (API) is a type of interface that helps specify the way components of a program work with each other. APIs are source code based. The API is part of libraries and frameworks. It defines many functions that are called upon.

In procedural languages (lists of step by step codes in C, Go, Fortran, Pascal, and BASIC), an API can specify functions that complete a certain task or interact with other components of the program. The functions will be used and say how to carry out their action in a library.

In object oriented languages (C++, C#, Java, etc..) API writes out how objects work together. It tends to take form as a set of classes and list of methods (blueprint of what to do), and it is functional when classes are implemented based on these 'requirements' in the API.

Build an API general with the future in mind so that parts are easily interchangeable, useful, and workable in the long term. Try to think hard and get it right the first time. It is easy to add functions, classes/methods, etc.. but you cannot take them out so add what is needed initially only. Extend it as needed and build on a good foundation. Keep names logical and self-explanatory. Try and keep a good system and use conventions to make it easier to work with others on the project.

Great API tips on building found: HERE.