The term collating sequence refers to the order in which character strings should be placed when sorting them. Sorting refers to a process of arranging items in some sequence and/or in different sets, and accordingly, it has two common, yet distinct meanings: ordering: aranging items of the same kind, class, nature, etc. ...

A common example is the familiar "alphabetic order," in which "Alfred" occurs before "Zeus" because "A" occurs before "Z" in the English alphabet. But there are other issues that a collating sequence must consider, say in a computer system.

• Upper and Lower-Case: Should "Alfred" be placed before or after "alfred"? Generally one would say "no," because an upper-case "A" and a lower-case "a" are usually considered to be the same letter. But it may be that you want to sort the records otherwise.
• National characters, accents, tildes: Various languages use these marks over and around letters, but once again the speakers of the language might consider the characters to be "the same."

In a computer system, each letter is necessarily assigned a unique numeric code (as in the ASCII or Unicode character set), but the proper and customary ordering of strings is not performed by a simple numeric comparison of those codes. Rather, the ordering is determined by reference to the collating sequence. There are 95 printable ASCII characters, numbered 32 to 126. ... Because of technical limitations, some web browsers may not display some special characters in this article. ... A character encoding is a code that pairs a set of characters (such as an alphabet or syllabary) with a set of something else, such as numbers or electrical pulses. ...