6.6 Global Installation

The user of a software is usually not interested in compiling or adapting the source code. Since it is quite difficult to run a software system from a development version a global binary installation can be made by VMake. The advantages of a global installation are:

1. All programs are in a fixed place and this directory can be added to the search path of the user. This information is stored in the environment variable PATH under UNIX or the logical DCL$PATH under VMS.
2. The installed version can be shared between different users in contrast to a private working version of a developer. This also reduces the memory requirements due to the fact, that the execution code of a program is shared between different invocations by the operating system. Only the data section is private to each invocation.
3. An installed version is built optimized similar to a production version and is therefore usually much faster than a working version which is usually compiled with debugging support.
4. No accidental changes can be made by the user to an installed version. Updates to a project can be only initiated by the corresponding developer. Ideally an installed version represents the status of a release or patch.
5. The size of an installed version is much smaller because there are no source files. Furthermore, any debugging information is removed.
6. An installed version of a project can be used as an external resource for the development of local projects.

During installation of a project an installation save file is created. This file is used for updating an installation to check for new, modified, or removed files. Unchanged files remain untouched in the installation. Obsolete files are deleted in the installation to reduce the used disc space. All installations are logged in the file ``projects.info'' in the root directory of the installation defined by the environment variable VROOT.

In contrast to other tools an installed version of a project can be used without any further developer interaction for development, too. The information from the project installation save file is parsed by VMake to get the information about all installed files and their dependences. This allows full checking of include dependences. For libraries correct expansion of all required libraries for program generation is possible. Using an installed project for development makes the local build process faster because the installation is used as an external resource without update actions. A local working project always overrides an installed version.