type Underflow

              object --+                        
                       |                        
exceptions.BaseException --+                    
                           |                    
        exceptions.Exception --+                
                               |                
        exceptions.StandardError --+            
                                   |            
          exceptions.ArithmeticError --+        
                                       |        
                        DecimalException --+    
                                           |    
                                     Inexact --+
                                               |
              object --+                       |
                       |                       |
exceptions.BaseException --+                   |
                           |                   |
        exceptions.Exception --+               |
                               |               |
        exceptions.StandardError --+           |
                                   |           |
          exceptions.ArithmeticError --+       |
                                       |       |
                        DecimalException --+   |
                                           |   |
                                     Rounded --+
                                               |
              object --+                       |
                       |                       |
exceptions.BaseException --+                   |
                           |                   |
        exceptions.Exception --+               |
                               |               |
        exceptions.StandardError --+           |
                                   |           |
          exceptions.ArithmeticError --+       |
                                       |       |
                        DecimalException --+   |
                                           |   |
                                   Subnormal --+
                                               |
                                              Underflow

Numerical underflow with result rounded to 0.

This occurs and signals underflow if a result is inexact and the adjusted exponent of the result would be smaller (more negative) than the smallest value that can be handled by the implementation (the value Emin). That is, the result is both inexact and subnormal.

The result after an underflow will be a subnormal number rounded, if necessary, so that its exponent is not less than Etiny. This may result in 0 with the sign of the intermediate result and an exponent of Etiny.

In all cases, Inexact, Rounded, and Subnormal will also be raised.