Patch

A patch refers to set of software modifications, typically applied to binaries by an installation program.

History
Early patches were often temporary additions to a piece of code, usually as a quick-and-dirty remedy to an existing bug. These patches may themselves contain bugs that are later corrected by other patches on top of them, leading to "scar tissue" within the original program. Some programmers anticipated this by leaving "patch space" within the code.

As the process became more formalized, IBM often delivered updates to their operating systems in the form of absolute patches. In October 1999, Apple Computer introduced Software Update in Mac OS 9 to deliver such updates, often still refered to as "patches", over the Internet. This update functionality is now handled by Apple's App Store for iOS, and the Mac App Store for macOS.