How does the use and purpose of a framework differ from a library in programming?

A framework and a library are tools for code reuse, but they differ in purpose and usage.

Library is a set of functions or classes that a developer calls at their discretion. The control flow of the program remains with the developer. For example, you can call a function from a library when needed.

Framework defines the architecture of the application and manages the flow of execution. You write code that the framework calls at the appropriate moments (the principle of "Inversion of Control"). The framework determines the structure of the application and its lifecycle.

Example: in Android SDK, the framework manages the lifecycle of an Activity by calling methods like onCreate, onStart, etc., and you implement the logic within these methods.

Thus, a library is a tool you use, while a framework is a structure into which you fit your code.