# 1.7 Application Program Interface (API) and Libraries

**Suggested Skills:** 4.A

**LO 1.7.A** — Identify the attributes and behaviors of a class found in the libraries contained in an API.

* **1.7.A.1** — **Libraries** are collections of classes. An **application programming interface (API)** specification informs the programmer how to use those classes. Documentation found in API specifications and libraries is essential to understanding the attributes and behaviors of a class defined by the API. A class defines a specific reference type. Classes in the APIs and libraries are grouped into packages. Existing classes and class libraries can be utilized to create objects.
* **1.7.A.2** — **Attributes** refer to the data related to the class and are stored in variables. **Behaviors** refer to what instances of the class can do (or what can be done with them) and are defined by methods.