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       - 
       
Click Create Datum
         
       to deactivate the History mode. 
       
         
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             - It will remain activated until you click on the icon again.
             
 
             - If you double-click this icon, the Datum mode is permanent. You 
             only have to click again the icon to deactivate the mode. 
 
             - A click on the icon activates the Datum mode for the current or 
             the next command. 
 
             - The History mode (active or inactive) will remain fixed from 
             one session to another: it is in fact a setting.
 
				- You can now activate both Repeat and Datum modes at the same 
				time. The original feature (i.e. the feature created without the 
				datum mode) is kept.
 
            
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