Genera is a commercial operating system and integrated development environment for Lisp machines created by Symbolics.

It is essentially a fork of an earlier operating system originating on the Massachusetts Institute of Technology (MIT) AI Lab's Lisp machines which Symbolics had used in common with Lisp Machines, Inc. (LMI), and Texas Instruments (TI).

Genera is an example of an object-oriented operating system based on the programming language Lisp.

It was a one-user workstation initially targeted at software developers for artificial intelligence (AI) projects.

[1] The system had a large bitmap screen, a mouse, a keyboard, a network interface, a disk drive, and slots for expansion.

The MIT Lisp machine operating system was developed from the middle 1970s to the early 1980s.

In 2006, the source code for this Lisp machine operating system from MIT was released as free and open-source software.

[2] Symbolics developed new Lisp machines and published the operating system under the name Genera.

Symbolics developed Genera based on this foundation of the MIT Lisp machine operating system.

Symbolics improved the operating system software from the original MIT Lisp machine and expanded it.

Its source code is more than a million lines; the number depends on the release and what amount of software is installed.

The user has free access to all parts of the running operating system and can write changes and extensions.

A patch is a file that can be loaded to fix problems or provide extensions to a particular version of a system.

Also, they made a new operating system named Minima for embedded uses, in Common Lisp.

All applications share one command line interpreter implementation, which adapts to various types of usage.

The user interface is mostly in monochrome (black-and-white) since that was what the hardware console typically provided.

The Dynamic Lisp Listener is an example of a command line interface with full graphics abilities and support for mouse-based interaction.

The Lisp listener can display forms to input data for the various built-in commands.

The documentation was created with a separate application that was not shipped with Genera: Symbolics Concordia.

The documentation provides user guides, installation guidelines and references of the various Lisp constructs and libraries.

Genera also provides access to, can read from and write to, other, local and remote, file systems including: NFS, FTP, HFS, CD-ROMs, tape drives.

It is remarkable that these programming language implementations inherited some of the dynamic features of the Lisp system (like garbage collection and checked access to data) and supported incremental software development.