J for Windows combines the language interpreter with a user interface called the session manager.
The session manager is a Windows multiple document interface (MDI) application, which allows the use of several document windows at one time within the same session. The session manager has a header, a menu line, Status Bar (which may be turned off), and one or more document windows.
You use the session manager by working with the document windows. You can have as many of these windows open as you wish - each window is attached to the same session. Only one window is active at a time.
There are two types of document window: execution windows and script windows:
Both window types represent ordinary files that can be saved during the session for use later on. Both are Windows edit controls, and you can use standard Windows commands to manipulate them, for example you can cut and paste between the windows and the Clipboard. You can move them about, resize them and minimize or maximize them.