Character (computing)

Internal representation of a single character (symbol, sequence of one or more bytes) used within a computer or system.
— Wikipedia

What represent character in computer?
Characters represent letters of the alphabet, punctuation, or other symbols (synonym for code point).

Example of characters can be found in ASCII note.

Characters are typically combined into ==strings==.

Historically character can be used to denote contiguous bits, size of character was various: 4, 5, 6, 8 bits (most popular). How modern systems implement characters?
All modern systems use a varying-size sequence of these fixed-sized pieces, for instance UTF-8 uses a varying number of 8-bit code units to define a “code point” and Unicode uses varying number of those to define a “character”.

Character sets, coded character sets, and encodings

Some notes from great w3.org character encodings article ¹.

A coded character set (unlike a character set) is a mapping, when each character assigned to unique number.

Units of a coded character set are known as code points, which represents the positon of a character. For example code point for the letter á in the Unicode coded character set is 225 in decimal, or 0xE1 in hexadecimal notation.

How character encoding connected with coded character set?
The character encoding reflects the way the coded character set is mapped to bytes for manipulation in a computer, some like characters ↔ bytes.

character encoding process.excalidraw

The process of character encoding

Is alphabet character always referring to single code point in Unicode?
Actually no, for user-perceived character (alphabet the smallest component) in complex scenarion may actually be a sequence of code points. For example, the Vietnamese letter ề will be perceived as a single letter even if the underlying code point sequence is U+0065 LATIN SMALL LETTER E + U+0302 COMBINING CIRCUMFLEX ACCENT + U+0300 COMBINING GRAVE ACCENT.

What is a grapheme cluster in Unicode?
A grapheme cluster is a collection of symbols that together represent an individual character that the user will see within a string on the screen. Sometimes need to use multiple grapheme clusters to represent one character (ক্ষ).

What is the relationship between glyphs and code points in a font system?
A font can be described as collection of glyphs. In simple scenario, a glyph is the visual representation of a code point. In fact, more than one glyph may be used to represent a single code point, and multiple code points may be represented by a single glyph (emoji character for “family” 👨‍👩‍👧‍👧).

Footnotes

1. Character encodings: Essential concepts ↩