What Is a Code Point?

T.S. Adams

Code point refers to a specific numerical value that signifies any individual character in a character set. From an end-user point of view, typing on a computer is rather simple; pressing a labeled key on the keyboard creates a corresponding character on the screen. However, from the computer's point of view, typing is far more difficult. The inputs from the keyboard must be translated several times in order to generate the specific chosen character. The code point of a specific character is just one step along the translation chain, resulting in visible on-screen text within a particular character set.

An example of a character set commonly used in computers is the American Standard Code for Information Interchange (ASCII).
An example of a character set commonly used in computers is the American Standard Code for Information Interchange (ASCII).

A character set is like a multilingual dictionary that explains to the computer which numbers correspond to which characters. A code point is the number corresponding to a particular character in that character set. Examples of character sets commonly used in computers include the American Standard Code for Information Interchange (ASCII) and Unicode. Each of these sets has a different set of code points, so while, for example, Code Point 400 in ASCII might refer to the "!" character, in Unicode it might refer to "&".

Once the end-user presses a button on the keyboard, the hardware generates a specific set of electronic impulses that the computer acts to convert into binary. Binary is the language of computers, which is comprised of nothing but the characters "1" and "0". From this, the computer calculates a specific number, which it must then match against the code point of the character set to generate the intended character. Only after all of this does the computer produce the selected character onscreen.

Code points are stored on the computer in spaces ranging from one to four bytes. This is a terribly small chunk of memory, meaning that storing hundreds or thousands of code points is no real challenge for modern computers. The result is that makers of character sets often leave large amounts of space open for unspecified code point assignments, allowing programmers to add additional characters to the set as necessary without making substantial revisions to the code.

Another point worth noting is that code points are most commonly used for abstract, or non-standard, characters in a character set. To see an example of these abstract characters, open the "Start" menu on the computer — if using a Windows-based machine — and type "Charmap" into the "Start Search" box. Press "Enter" to display a list of the available abstract characters for a chosen character set.

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