Visual Source Safe

Visual SourceSafe is the ideal version control system for any development team using Microsoft Visual Studio .NET.A file stored in a VSS server is not available via the standard file system, instead, it must be accessed through the VSS client tools - the VSS windows client, the VSS command-line tool, or else some application which integrates with or emulates these client tools.
VSS Database
A VSS Database is a single instance of a VSS server - it's the big black box into which files get placed. All commands to VSS are directed towards a particular VSS Database, and wach database maintains a SRCSAFE.INI file which contains configuration information.

VSS Project
A VSS Database is organised as a tree structure, with each of the nodes of the tree being a VSS Project. Each database contains a single root project, which can branch (to a depth of 15 nodes) into sub-projects.

Working Folder
Because the files stored in VSS are not directly exposed as files, development work on these files takes place on local copies, which are first checked out of VSS, changed, then checked in again. While a file is checked out of VSS, it is can be locked to other developers, preventing file overwriting. VSS also retains historical information about a file's changes, so it is possible to extract and use old versions of a file, or roll back unsuccessful changes. The folder in which a user manipulates his local copy of VSS project files is known as his 'working folder'. Each user will often have a distinct, local working folder for each VSS project, the details of which are held by the VSS client in its SS.INI file. Each working folder also gets populated with a VSSVER.SCC file, which contains version information about the files in that folder. This allows VSS quickly to determine whether or not local files are synchronised with those stored in the VSS database.

Check out
when you 'Check out' a file / project , a writable copy is placed into your working folder. By default, this locks the file to other users, so that while they may 'Get' a copy of the file they cannot themselves check it out. Notice that when you check out (and check in), you have the option to add a comment. This is to help developers keep track of the file changes.

Checking In
When you've finished making changes to a checked-out file / project, then you can check it in again, which writes the file changes to the VSS database. This procedure is also effected in the client tools using a right-click menu. By checking project files out and in using VSS, developers can avoid the situation in which one overwrites the changes made by another.