{{Sorting Algorithm}}
[[Category:Sorting]]

When sorting records in a table by a particular column or field, a [[wp:Stable_sort#Stability|stable sort]] will always retain the  relative order of records that have the same key.


;Example:
In this table of countries and cities, a stable sort on the ''second'' column, the cities, would keep the &nbsp; '''US&nbsp;Birmingham''' &nbsp; above the &nbsp; '''UK&nbsp;Birmingham'''. 

(Although an unstable sort ''might'', in this case, place the &nbsp; '''US&nbsp;Birmingham''' &nbsp; above the &nbsp; '''UK&nbsp;Birmingham''', &nbsp; a stable sort routine would ''guarantee'' it).

<pre>
UK  London
US  New York
US  Birmingham
UK  Birmingham
</pre>

Similarly, stable sorting on just the first column would generate '''UK&nbsp;London''' as the first item and '''US&nbsp;Birmingham''' as the last item &nbsp; (since the order of the elements having the same first word – &nbsp; '''UK''' or '''US''' &nbsp; – would be maintained).


;Task:
:# &nbsp; Examine the documentation on any in-built sort routines supplied by a language.
:# &nbsp; Indicate if an in-built routine is supplied
:# &nbsp; If supplied, indicate whether or not the in-built routine is stable.

<br>
(This [[wp:Stable_sort#Comparison_of_algorithms|Wikipedia table]] shows the stability of some common sort routines).
<br><br>
