Subroutine package

A subroutine package (often called a 'library') is a group of subroutines which support some particular functionality.

For example, on early machines which did not support floating point in hardware, it was common to have a floating point library. For commercial applications, which often use binary-coded decimal for arbitrary-precision numbers, a library implementing them was often provided on machines which lacked hardware support for BCD.

In the C programming language, which does not include input/output as part of the language, the standard I/O library is a portable library which provides a standard way to perform I/O on many systems which C runs on.