Quick Fix Engineering (QFE) is a Microsoft term for the delivery of individual service updates to its operating systems and application programs such as Word. Formerly called a hotfix, "QFE" can be used to describe both the method of delivering and applying a patch or fix, and also to refer to any individual fix. Because of the complexity and sheer number of lines of code in most application programs and operating systems, the delivery of temporary fixes to users has long been provided by major software manufacturers. Typically, not all fixes are necessarily applied by an enterprise since they can occasionally introduce new problems. All of the fixes in any given system are usually incorporated (so they don't have to be reapplied) whenever a new version of a program or operating system comes out.
Periodically, all current QFEs (or hotfixes) are delivered together as a service pack, which can be applied more efficiently than applying fixes one at a time.