A watch allows you to monitor the values of variables, properties, and expressions at runtime. These watch expressions appear in the Watch window, which lets you observe their values. As mentioned above, you may also use watch expressions to switch the application into Break mode whenever the expression’s value changes or equals a specified value. For example, you may use a watch expression to put the application in Break mode when a loop counter reaches a specific value, or you may want the application to enter Break mode whenever a flag in a procedure changes value. Watch variables allow you to change the display format of variables in the Watch window or the Quick Watch dialog box using formatting symbols. Watches can only be added during design time or while the program is in Break mode