An application directory is a grouping of

software Software is a set of computer programs and associated software documentation, documentation and data (computing), data. This is in contrast to Computer hardware, hardware, from which the system is built and which actually performs the work. ...

code, help files and resources that together comprise a complete software package but are presented to the user as a single object. They are currently used in

RISC OS RISC OS is a computer operating system originally designed by Acorn Computers Ltd in Cambridge, England. First released in 1987, it was designed to run on the ARM chipset, which Acorn had designed concurrently for use in its new line of Archi ...

and the

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, and also form the basis of the

Zero Install Zero Install is a means of distributing and packaging software for multiple operating systems (Unix-like including Linux and macOS, Windows). Software Rather than the normal method of downloading a software package, extracting it, and install ...

application distribution system. Similar technology includes

VMware ThinApp VMware ThinApp (formerly ''Thinstall'') is an application virtualization and portable application creator suite by VMware that can package conventional Windows applications so that they become portable applications by running on another operat ...

, and the

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GNUstep GNUstep is a free software implementation of the Cocoa (formerly OpenStep) Objective-C frameworks, widget toolkit, and application development tools for Unix-like operating systems and Microsoft Windows. It is part of the GNU Project. GNUste ...

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concept of application bundles. Their heritage lies in the system for automatically launching software stored on floppy disk on Acorn's earlier 8-bit micros such as the

BBC Micro The British Broadcasting Corporation Microcomputer System, or BBC Micro, is a series of microcomputers and associated peripherals designed and built by Acorn Computers in the 1980s for the BBC Computer Literacy Project. Designed with an emphas ...

(the ''!BOOT'' file). Bundling various files in this manner allows tools for manipulating applications to be replaced by tools for manipulating the file system. Applications can often be "installed" simply by dragging them from a distribution medium to a hard disk, and "uninstalled" by deleting the application directory.

Fixed contents

In order to support user interaction with application directories, several files have special status.

Application binaries

Launching an application directory causes the included file ''AppRun'' (ROX Desktop) or ''!Run'' (RISC OS) to be launched. On RISC OS this is generally an Obey file (a RISC OS command script) which allocates memory and loads OS extension modules and

shared libraries In computer science, a library is a collection of non-volatile resources used by computer programs, often for software development. These may include configuration data, documentation, help data, message templates, pre-written code and su ...

before executing the application binary, usually called ''!RunImage''. Under the ROX Desktop, it is not uncommon for it to be a shell script that will launch the correct system binary if available or compile a suitable binary from source otherwise.

Help files and icons

Both RISC OS and the ROX Desktop allow the user to view help files associated with an application directory without launching the application. RISC OS relies on a file in the directory named ''!Help'' which is launched as if the user double-clicked on it when help is requested (and can be any format the system understands, but plain text and !Draw formats are common), while the ROX Desktop opens the application's ''Help'' subdirectory. Similarly, custom icons for the Application Directory may be contained within it—either ''.DirIcon'' (in any supported image format) or ''AppIcon.xpm'' under the ROX Desktop, or ''!Sprites'' and optionally ''!Sprites22'' under RISC OS. The RISC OS Filer automatically loads these sprite files in the absence of a ''!Boot'' file, otherwise it is left to the ''!Boot'' file to load the appropriate icons.

!Boot

RISC OS application directories may contain a file named ''!Boot'' which is executed by the ''Filer'' either explicitly via the FilerBoot command, or when the bundle is first displayed (unless the user held

Control Control may refer to: Basic meanings Economics and business * Control (management), an element of management * Control, an element of management accounting * Comptroller (or controller), a senior financial officer in an organization * Controllin ...

when opening that ''Filer'' window, which defeats application booting). This allows an application to do tasks such as register supported filetypes (by defining their name, setting command aliases for running or printing them and loading appropriate icons), or choose to load different icons such as ''ASprites'' (icons with an alpha channel for RISC OS Select), ''5Sprites'' (icons with a RISC OS 5 appearance) or theme-specific icons. ''!Boot'' files are the most popular propagation

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for such RISC OS

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es as exist (such as the well-known Extend virus), though they can be defeated simply by holding ''Control''. The ''!Boot'' feature is not duplicated by the ROX Desktop.

The RISC OS !Boot system directory

Acorn's early machines allowed a medium to be "booted" (automatically run) by executing a file called ''!BOOT'' if present (this action, "booting a disc", was toggled with the Shift, and hence became known as ''shift-booting''). This was exploited in the RISC OS disc structure by having an application directory in the root of the default disc called ''!Boot''. This ''application directory'' is executed (run) when the machine boots (if so configured), therefore causing its !Run file to be executed (i.e. ''$.!Boot.!Run'' in Acorn

pathname A path is a string of characters used to uniquely identify a location in a directory structure. It is composed by following the directory tree hierarchy in which components, separated by a delimiting character, represent each directory. The del ...

syntax). This file then causes various files to be executed, OS modules loaded, standard icons to be loaded and filetypes defined, and defines a number of standard variables through which its various subdirectories are accessed. Thus RISC OS's entire boot sequence can be avoided merely by holding Shift.

Notes

{{Reflist

External links

ROX-Filer User Manual: Application directories
Software distribution Source code