In the world of software development, maintenance mode refers to a point in a program

Computer program

A computer program is a sequence of instructions written to perform a specified task with a computer. A computer requires programs to function, typically executing the program's instructions in a central processor. The program has an executable form that the computer can use directly to execute...

's life when it has reached all of its goals and is generally considered to be "complete" and bug-free. Continued development is deemed unnecessary or ill-advised, but occasional bug fixes and security patch

Patch (computing)

A patch is a piece of software designed to fix problems with, or update a computer program or its supporting data. This includes fixing security vulnerabilities and other bugs, and improving the usability or performance...

es are still issued, hence the term maintenance mode. Maintenance mode often transitions to abandonware

Abandonware

Abandonware are discontinued products for which no product support is available, or whose copyright ownership may be unclear for various reasons...

.

Sometimes, when a popular free software

Free software

Free software, software libre or libre software is software that can be used, studied, and modified without restriction, and which can be copied and redistributed in modified or unmodified form either without restriction, or with restrictions that only ensure that further recipients can also do...

 project undergoes a major overhaul, the pre-overhaul version is kept active and put into maintenance mode because it will still be widely used in production for the foreseeable future. Project forks

Fork (software development)

In software engineering, a project fork happens when developers take a legal copy of source code from one software package and start independent development on it, creating a distinct piece of software...

 can also spawn from programs that go into maintenance mode too soon or have enough developer support for a more advanced version. A good example of this is the vi

Vi

vi is a screen-oriented text editor originally created for the Unix operating system. The portable subset of the behavior of vi and programs based on it, and the ex editor language supported within these programs, is described by the Single Unix Specification and POSIX.The original code for vi...

 editor, which was in maintenance mode and forked into Vi IMproved

Vim (text editor)

Vim is a text editor written by Bram Moolenaar and first released publicly in 1991. Based on the vi editor common to Unix-like systems, Vim is designed for use both from a command line interface and as a standalone application in a graphical user interface...

. The Vim fork has many useful features that vi does not, such as syntax highlighting

Syntax highlighting

Syntax highlighting is a feature of some text editors that display text—especially source code—in different colors and fonts according to the category of terms. This feature eases writing in a structured language such as a programming language or a markup language as both structures and...

 and the ability to have multiple open buffer

Buffer (computer science)

In computer science, a buffer is a region of a physical memory storage used to temporarily hold data while it is being moved from one place to another. Typically, the data is stored in a buffer as it is retrieved from an input device or just before it is sent to an output device...

s.