Editing Plan 9 from Bell Labs (section)

== Software for Plan 9 ==
{{Further|List of Plan 9 applications}}
As a benefit from the system's design, most tasks in Plan 9 can be accomplished by using [[ls]], [[Cat (Unix)|cat]], [[grep]], [[cp (Unix)|cp]] and [[rm (Unix)|rm]] utilities in combination with the [[rc shell]] (the default Plan 9 shell).

[[Factotum (software)|Factotum]] is an [[authentication server|authentication]] and [[key management]] server for Plan 9. It handles authentication on behalf of other programs such that both [[secret key]]s and implementation details need only be known to Factotum.<ref name="auth-paper" />

=== Graphical programs ===
[[File:Plan 9 from Bell Labs (with acme).png|thumb|right|Plan 9 running [[acme (text editor)|acme]] and rc]]
Unlike [[Unix]], Plan 9 was designed with graphics in mind.<ref name="not_dead" /> After booting, a Plan 9 terminal will run the [[rio (windowing system)|rio]] windowing system, in which the user can create new windows displaying [[Rc (Unix shell)|rc]].<ref name="osnews-investigating" /> Graphical programs invoked from this shell replace it in its window.

The [[plumber (Plan 9)|plumber]] provides an [[inter-process communication]] mechanism which allows system-wide hyperlinking.

[[sam (text editor)|Sam]] and [[acme (text editor)|acme]] are Plan 9's text editors.<ref name="usethis-interview-russ-cox" />

=== Storage system ===
Plan 9 supports the [[Kfs]], [[PAQ|Paq]], [[Cwfs]], [[File Allocation Table|FAT]], and [[Fossil (file system)|Fossil]] file systems. The last was designed at Bell Labs specifically for Plan 9 and provides snapshot storage capability. It can be used directly with a hard drive or backed with [[Venti (software)|Venti]], an archival file system and permanent data storage system.

=== Software development ===
The distribution package for Plan 9 includes special compiler variants and programming languages, and provides a tailored set of libraries along with a windowing [[user interface]] system specific to Plan 9.<ref name="Dixon2004" /> The bulk of the system is written in a dialect of C ([[ANSI C]] with some extensions and some other features left out). The compilers for this language were custom built with portability in mind; according to their author, they "compile quickly, load slowly, and produce medium quality object code".<ref name="auug-new-c-compiler" />

A [[concurrent programming language]] called [[Alef (programming language)|Alef]] was available in the first two editions, but was then dropped for maintenance reasons and replaced by a [[Thread (computing)|threading]] library for C.<ref>{{cite web|last=Pike|first=Rob|title=Rio: Design of a Concurrent Window System|url=http://doc.cat-v.org/plan_9/3rd_edition/rio/rio_slides.pdf|access-date=8 March 2013}}</ref><ref>{{man|2|thread|Plan 9}}</ref>

=== Unix compatibility ===
Though Plan 9 was supposed to be a further development of Unix concepts, compatibility with preexisting Unix software was never the goal for the project. Many [[command-line utilities]] of Plan 9 share the names of Unix counterparts, but work differently.<ref name="unix-plan9-command-translation" />

Plan 9 can support [[POSIX]] applications and can emulate the [[Berkeley socket interface]] through the [[ANSI/POSIX Environment]] (APE) that implements an [[runtime environment|interface]] close to [[ANSI C]] and [[POSIX]], with some common extensions (the native Plan 9 C interfaces conform to neither standard). It also includes a POSIX-compatible shell. APE's authors claim to have used it to port the [[X Window System]] (X11) to Plan 9, although they do not ship X11 "because supporting it properly is too big a job".<ref name="docs-ape" /> Some Linux binaries can be used with the help of a "linuxemu" (Linux emulator) application; however, it is still a work in progress.<ref name="linuxemu" /> Vice versa, the [[Vx32]] virtual machine allows a slightly modified Plan 9 kernel to run as a user process in Linux, supporting unmodified Plan 9 programs.{{r|vx32}}