Installation refers to the particular configuration of software or hardware with a view to making it usable with the computer.
[1] Installation typically involves code (program) being copied/generated from the installation files to new files on the local computer for easier access by the operating system, creating necessary directories, registering environment variables, providing a separate program for un-installation etc.
Because code is generally copied/generated in multiple locations, uninstallation usually involves more than just erasing the program folder.
For example, registry files and other system code may need to be modified or deleted for a complete uninstallation.
Other programs are supplied in a form unsuitable for immediate execution and therefore need an installation procedure.
This was once usual for many programs which run on DOS, the classic Mac OS, Atari TOS and AmigaOS.
As computing environments grew more complex and fixed hard drives replaced floppy disks, the need for tangible installation presented itself.
The modern applications that can be run without going through formal process of installation and, in particular, do not require modifications of the operating system, are sometimes referred to as zero-install.
Similarly, there are live operating systems, which do not need installation and can be run directly from a bootable CD, DVD, USB flash drive or loaded over the network as with thin clients.
An installation process usually needs a user who attend it to make choices, such as accepting or declining an end-user license agreement (EULA), specifying preferences such as the installation location, supplying passwords or assisting in product activation.
A common misconception is unarchivation, which is not considered an installation action because it does not include user choices, such as accepting or declining EULA.
Malware and viruses can be installed silently when a person clicks on a link while working at a business they think is real but is a hacker's program download.
Silently installing a software program can be used to deploy a program on networks in educational institutions, including primary and secondary education and universities, in addition to business, government, and corporate networks.
Windows XP and most Linux distributions are examples of operating systems that can be installed with an answer file.
For example, the infamous Con ficker was installed when the user plugged an infected device to their computer.
This may simply be a copy of the original media but software publishers which offer site licenses for institutional customers may provide a version intended for installation over a network.
An instance of native code is InstallAware Multi Platform by InstallAware Software, featuring build toolchains and a setup engine that runs without dependencies; it can also switch to console mode if a graphical user interface (GUI) cannot be displayed on Linux.
Examples include InstallShield (Flexera Software), WiX (Outercurve Foundation) and Advanced Installer.
These often feature prominent installation instructions and a shortcut to the Applications folder; that style of drag-install application was invented and published by Iris Artin (formerly Ben Artin) during the development of Fetch 5[14] and subsequently gained wide adoption.