Handling a Project by Several Programmers
When several programmers are working with the same project, they normally use some source code control systems (SCS) like SourceGear Vault, Microsoft Visual SourceSafe, etc.
A source code control system is a program for maintaining version control of source files being developed. It allow members of your development team to retrieve, modify, and return any revision of a file in a secure, systematic, and compatible manner. With SCS you minimize the risk of overwriting changes made by another developer and you do not have to worry about losing data, because all changes are easily accessible.
Using the SCS from IDE
You can tune IDE to handle the Check Out and Check In commands of the SourceGear Vault or Microsoft Visual SourceSafe (or similar commands in other Source Control Systems). When you add Check Out and Check In commands (with Tools | Configure Tools) to IDE commands, then you will be able to Check In and Check Out edited files into the Source Control System database (Repository) by pressing some simple hot key like Ctrl+1. The detailed description of how to add Check Out and Check In commands to IDE commands see in "How to "Check In" a File in MS Visual Source Safe" and "How to "Check Out" and "Check In" a File in Vault".
Defining the Source Control Repository
If you are using a Source Control System, then Tools | Source Control Repository... menu entry can be used to configure a SCS repository. Here you can set a repository name and the correspondent working folder which will be used for this repository. This will define values for variables $(repsitory) and $(scfile) for the tools (like the Check Out command).
Additionally, Tools | IDE Variables menu entry can be used to configure other SCS parameters, like user name (variable $(user)), host name (variable $(host)) and password (varaible $(password)).