CatTools can be run either as a Windows service or as a standard Windows application.
To run CatTools as a standard application you must first be logged in as a Windows user. You can then start the application and interact with the user interface.
To run CatTools as a service, it must be installed to the Windows Service Manager. You can do this from the CatTools Manager application. A service is an application that Windows starts and runs independent of whether a user is logged on or not. The application starts when Windows starts and terminates when Windows shuts down.
Services interact with the machine according to different rules from a standard application. A standard application is able to run according to the limitations of the user who is logged in at the time. A service by default runs under a special account known as the local system account, which normally has many restrictions in terms of file permissions and the like.
A service can be installed to run under a specified user account. It can then run according to that account's rules and permissions. However, it then cannot interact with the system console. See Viewing the CatTools Service interface for more details.