Sorting is a way of arranging a group of things in a specified order. Normally, the order is a "natural order." Examples of natural orders are counting order or alphabetical order. In computing, time and memory usage are of concern when sorting. Some algorithms are very fast, but use a lot of memory, or vice versa. Usually, speed has higher priority. The speed of an algorithm is often determined by the number of compares and/or swaps required. This is denoted as its "order" and is shown in Big O notation. For example, a Quicksort is usually noted for being of "order n log n" (where n is the size of the group). This shown in Big O notation as "O(n log(n))." Sorting algorithms often have different orders depending on characteristics of the group being sorted. For example, the Quicksort will perform at O(n^2) when the group is already ordered. A sort which "swaps" elements within the group is called an "in-place sort." A sort which moves elements to another group, destroys, or simply ignores the original group is sometimes called an "out-of-place sort" or a "not-in-place sort." An example of an out-of-place sort is the counting sort.
For complete implementations of various sorting algorithms, see Category:Sorting Algorithms.
For examples of how to use sorting functionality provided by a language, see: