Portable application - AbsoluteAstronomy.com

A portable application sometimes also called standalone, is a computer

Computer

A computer is a programmable machine designed to sequentially and automatically carry out a sequence of arithmetic or logical operations. The particular sequence of operations can be changed readily, allowing the computer to solve more than one kind of problem...

software program designed to run independently from an operating system. This type of application is stored on a removable storage device such as a CD

Compact Disc

The Compact Disc is an optical disc used to store digital data. It was originally developed to store and playback sound recordings exclusively, but later expanded to encompass data storage , write-once audio and data storage , rewritable media , Video Compact Discs , Super Video Compact Discs ,...

, USB flash drive

USB flash drive

A flash drive is a data storage device that consists of flash memory with an integrated Universal Serial Bus interface. flash drives are typically removable and rewritable, and physically much smaller than a floppy disk. Most weigh less than 30 g...

, flash card

Flash memory

Flash memory is a non-volatile computer storage chip that can be electrically erased and reprogrammed. It was developed from EEPROM and must be erased in fairly large blocks before these can be rewritten with new data...

, or floppy disk

Floppy disk

A floppy disk is a disk storage medium composed of a disk of thin and flexible magnetic storage medium, sealed in a rectangular plastic carrier lined with fabric that removes dust particles...

– storing its program files, configuration information and data on the storage medium alone.

Portable applications can be run on any computer system with which they are compatible but typically require a specific operating system

Operating system

An operating system is a set of programs that manage computer hardware resources and provide common services for application software. The operating system is the most important type of system software in a computer system...

(such as Microsoft Windows

Microsoft Windows

Microsoft Windows is a series of operating systems produced by Microsoft.Microsoft introduced an operating environment named Windows on November 20, 1985 as an add-on to MS-DOS in response to the growing interest in graphical user interfaces . Microsoft Windows came to dominate the world's personal...

XP or above, certain version of a Linux

Linux

Linux is a Unix-like computer operating system assembled under the model of free and open source software development and distribution. The defining component of any Linux system is the Linux kernel, an operating system kernel first released October 5, 1991 by Linus Torvalds...

distro, etc.)

Depending on the operating system, portability is more or less complex to implement; to operating systems such as AmigaOS

AmigaOS

AmigaOS is the default native operating system of the Amiga personal computer. It was developed first by Commodore International, and initially introduced in 1985 with the Amiga 1000...

, all applications are by definition portable. Portable apps are distinct from software portability
Software portability
Portability in high-level computer programming is the usability of the same software in different environments. The prerequirement for portability is the generalized abstraction between the application logic and system interfaces...

where software allows its source code

Source code

In computer science, source code is text written using the format and syntax of the programming language that it is being written in. Such a language is specially designed to facilitate the work of computer programmers, who specify the actions to be performed by a computer mostly by writing source...

to be compiled

Compiler

A compiler is a computer program that transforms source code written in a programming language into another computer language...

for different computing platforms.

Portable Windows applications

A portable application does not leave its files or settings on the host computer. Typically the application does not write to the Windows registry

Windows registry

The Windows Registry is a hierarchical database that stores configuration settings and options on Microsoft Windows operating systems. It contains settings for low-level operating system components as well as the applications running on the platform: the kernel, device drivers, services, SAM, user...

or store its configuration files (such as an INI file) in the user's profile

Home directory

A Home directory is a file system directory on a multi-user operating system containing files for a given user of the system. The specifics of the home directory is defined by the operating system involved; for example, Windows systems between 2000 and 2003 keep home directories in a folder...

; instead, it stores its configuration files in the program's directory. Another requirement, since file paths

Path (computing)

A path, the general form of a filename or of a directory name, specifies a unique location in a file system. A path points to a file system location by following the directory tree hierarchy expressed in a string of characters in which path components, separated by a delimiting character, represent...

will often differ on changing computers due to variation in Windows drive letter assignments

Drive letter assignment

Drive letter assignment is the process of assigning alphabetical identifiers to physical or logical disk drives or partitions in the root filesystem namespace; this usage is now mostly found in Microsoft operating systems...

, is the need for applications to store them in a relative format. While some applications have options to support this behavior, many programs are not designed to do this. A common technique for such programs is the use of a launcher program to copy necessary settings and files to the host computer when the application starts and move them back to the application's directory when it closes.

An alternative strategy for achieving application portability within Windows, without requiring application source code changes, is application virtualization

Application Virtualization

Application virtualization is an umbrella term that describes software technologies that improve portability, manageability and compatibility of applications by encapsulating them from the underlying operating system on which they are executed. A fully virtualized application is not installed in...

: An application is "sequenced" or "packaged" against a runtime layer that transparently intercepts its file system and registry calls, then redirects these to other persistent storage without the application's knowledge. This approach leaves the application itself unchanged, yet portable.

The same approach is used for individual application components: run-time libraries, COM

Component Object Model

Component Object Model is a binary-interface standard for software componentry introduced by Microsoft in 1993. It is used to enable interprocess communication and dynamic object creation in a large range of programming languages...

components or ActiveX

ActiveX

ActiveX is a framework for defining reusable software components in a programming language-independent way. Software applications can then be composed from one or more of these components in order to provide their functionality....

, not only for the entire application. As a result, when individual components are ported in such manner they are able to be: integrated into original portable applications, repeatedly instantiated (virtually installed) with different configurations/settings on the same operating system

Operating system

(OS) without mutual conflicts. As the ported components do not affect the OS-protected related entities (registry and files), the components will not require administrative privileges for installation and management.

Microsoft saw the need for an application-specific registry for its Windows operating system as far back as 2005. It eventually incorporated some of this technology, using the techniques mentioned above, via its Application Compatibility Database using its Detours code library, into Windows XP. It did not, however, make any of this technology available via one of its system APIs.

Portability on Linux and UNIX-like systems

Programs written with a Unix-like base in mind often do not make any assumptions. Whereas many Windows programs assume the user is an administrator

Superuser

On many computer operating systems, the superuser is a special user account used for system administration. Depending on the operating system, the actual name of this account might be: root, administrator or supervisor....

—something very prevalent in the days of Windows 95

Windows 95

Windows 95 is a consumer-oriented graphical user interface-based operating system. It was released on August 24, 1995 by Microsoft, and was a significant progression from the company's previous Windows products...

/98

Windows 98

Windows 98 is a graphical operating system by Microsoft. It is the second major release in the Windows 9x line of operating systems. It was released to manufacturing on 15 May 1998 and to retail on 25 June 1998. Windows 98 is the successor to Windows 95. Like its predecessor, it is a hybrid...

/ME

Windows Me

Windows Millennium Edition, or Windows Me , is a graphical operating system released on September 14, 2000 by Microsoft, and was the last operating system released in the Windows 9x series. Support for Windows Me ended on July 11, 2006....

(and to some degree in Windows XP

Windows XP

Windows XP is an operating system produced by Microsoft for use on personal computers, including home and business desktops, laptops and media centers. First released to computer manufacturers on August 24, 2001, it is the second most popular version of Windows, based on installed user base...

/2000

Windows 2000

Windows 2000 is a line of operating systems produced by Microsoft for use on personal computers, business desktops, laptops, and servers. Windows 2000 was released to manufacturing on 15 December 1999 and launched to retail on 17 February 2000. It is the successor to Windows NT 4.0, and is the...

, though not in Windows Vista

Windows Vista

Windows Vista is an operating system released in several variations developed by Microsoft for use on personal computers, including home and business desktops, laptops, tablet PCs, and media center PCs...

)—such would quickly result in "Permission denied" errors in Unix-like environments since users will be in an unprivileged state much more often. Programs are therefore generally designed around using the HOME environment variable to store settings (e.g. $HOME/.w3m for the w3m

W3m

w3m is a free software/open source text-based web browser. It has support for tables, frames, SSL connections, color and inline images on suitable terminals...

browser). The dynamic linker provides an environment variable LD_LIBRARY_PATH that programs can use to load libraries from non-standard directories. Assuming /mnt contains the portable programs and configuration, a command line may look like:

HOME=/mnt/home/user LD_LIBRARY_PATH=/mnt/usr/lib /mnt/usr/bin/w3m www.example.com

A linux application without need for a user-interaction (e.g. adapting a script or environment variable) on varying directory paths can be achieved with the GCC

GNU Compiler Collection

The GNU Compiler Collection is a compiler system produced by the GNU Project supporting various programming languages. GCC is a key component of the GNU toolchain...

Linker

In computer science, a linker or link editor is a program that takes one or more objects generated by a compiler and combines them into a single executable program....

option $ORIGIN which allows a relative library search path.

Not all programs honor this – some completely ignore $HOME and instead do a user lookup in /etc/passwd to find the home directory, therefore thwarting portability.

Some Linux distributions already have native support for portable apps (Super OS, with RUNZ files).

There are also cross-distro package formats that don't require installation or admin rights to run.

Portable Windows applications

Portability on Linux and UNIX-like systems

See also