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2 Languages
3 Interface Reference
4 Extending Dr Scheme
On this page:
3.4.1 Program Files
3.4.2 Backup and Autosave Files
3.4.3 Preference Files
Version: 4.0.2


3.4 DrScheme Files

3.4.1 Program Files

The standard file extension for a PLT Scheme program file is ".ss". The extensions ".scm" and ".sch" are also popular.

DrScheme’s editor can save a program file in two different formats:

3.4.2 Backup and Autosave Files

When you modify an existing file in DrScheme and save it, DrScheme copies the old version of the file to a special backup file if no backup file exists. The backup file is saved in the same directory as the original file, and the backup file’s name is generated from the original file’s name:

When a file in an active DrScheme editor is modified but not saved, DrScheme saves the file to a special autosave file after five minutes (in case of a power failure or catastrophic error). If the file is later saved, or if the user exists DrScheme without saving the file, the autosave file is removed. The autosave file is saved in the same directory as the original file, and the autosave file’s name is generated from the original file’s name:

If the definitions window is modified and there is no current file, then an autosave file is written to the user’s “documents” directory.

The “documents” directory is determined by (find-system-path 'doc-dir).

3.4.3 Preference Files

On start-up, DrScheme reads configuration information from a preferences file. The name and location of the preferences file depends on the platform and user:

The expression (find-system-path 'pref-file) returns the platform- and user-specific preference file path.

A lock file is used while modifying the preferences file, and it is created in the same directory as the preferences file. Under Windows, the lock file is named "_LOCKplt-prefs.ss"; under Unix, it is ".LOCK.plt-prefs.ss"; under Mac OS X, it is ".LOCK.org.plt-scheme.prefs.ss".

If the user-specific preferences file does not exist, and the file "plt-prefs.ss" in the "defaults" collection does exist, then it is used for the initial preference settings. (See Libraries and Collections for more information about collections.) This file thus allows site-specific configuration for preference defaults. To set up such a configuration, start DrScheme and configure the preferences to your liking. Then, exit DrScheme and copy your preferences file into the "defaults" collection as "plt-prefs.ss". Afterward, users who have no preference settings already will get the preference settings that you chose.