Code point
A code point is a numeric value assigned by a character-representation standard to identify an abstract character or symbol.
Modern C, Third Edition
A code point is a numeric value identifying a character or abstract symbol in a character repertoire such as Unicode.
- How it is used
- Uses code points to distinguish Unicode characters from their glyphs and encoded representations in C text and identifiers.
- How deep it goes
- Defines the character concept and works through escapes, UTF element counts, normalization, and incomplete multibyte input.
- Examples
- Uses box-drawing escapes, an accented letter, and UTF-16 and UTF-32 literals for `𝒜`.
- What you can do after
- Apply it via C escapes and restartable conversion to represent characters and recognize complete multibyte input.
Modern C
A code point is a numeric value assigned by a character standard to a character concept.
- How it is used
- Identifies character concepts when writing extended characters in C multibyte strings.
- How deep it goes
- Defines the distinction from glyphs and works through C11 escape syntax without detailing the resulting byte encoding.
- Examples
- Uses \u00E4 for ä and escaped box-drawing characters in C macros.
- What you can do after
- Apply it via C11 \u and \U escapes to specify Unicode characters in multibyte strings.
Julia as a Second Language
A code point is a numeric value assigned to an abstract character or other element in a coded character set.
- How it is used
- Clarifies why multilingual Julia strings cannot be treated as one byte per character.
- How deep it goes
- Works through numeric identifiers, variable-width storage, and string iteration; shows only an excerpt of `nextind` internals.
- Examples
- Demonstrates `A`, `Æ`, and an emoji in REPL calls, then iterates a multilingual string with skipped indices.
- What you can do after
- Apply Julia’s `codepoint`, `ncodeunits`, and `nextind` to distinguish character identity from storage and traverse strings.
100 Java Mistakes and How to Avoid Them
A Unicode code point is a numeric value identifying an abstract character or character-related symbol in the Unicode character set.
- How it is used
- Prevents Unicode text processing from confusing UTF-16 code units with displayed characters.
- How deep it goes
- Explains surrogate pairs, combining characters, failure effects, and Java alternatives, but does not fully define grapheme segmentation.
- Examples
- Uses emoji, skin-tone modifiers, fixed-row string splitting, digit checks, code-point streams, and BreakIterator.
- What you can do after
- Apply it via Java codePointAt(), codePoints(), and BreakIterator when processing Unicode text safely.
Read how 100 Java Mistakes and How to Avoid Them explains code point →
100 Go Mistakes and How to Avoid Them
A Unicode code point is a numeric value that identifies an abstract character or symbol in the Unicode standard.
- How it is used
- Explains why Go string operations can confuse byte counts, rune counts, and character-oriented behavior.
- How deep it goes
- Defines code points, contrasts them with encodings, and traces UTF-8 byte length before stopping at broader string operations.
- Examples
- Uses 汉, U+6C49, its three UTF-8 bytes, and len("汉") to expose byte-versus-rune counting.
- What you can do after
- Apply rune-aware iteration and indexing while diagnosing incorrect assumptions about Go string length or encoding.
Read how 100 Go Mistakes and How to Avoid Them explains code point →
API Design Patterns
A Unicode code point is a numeric value assigned by Unicode to identify a character or other encoded abstract element.
- How it is used
- Defines a practical unit for string-length limits and explains why Unicode representations matter for web-API identifiers.
- How deep it goes
- Explains code-point counting, UTF-32 sizing, normalization ambiguity, and ASCII recommendations without developing Unicode normalization in detail.
- Examples
- Uses “á” as both a single code point and a composed sequence to expose representation differences.
- What you can do after
- Apply code-point-aware limits, estimate storage conservatively, reject overlong strings, and choose ASCII for unique identifiers.
Related concepts
- runeequivalent to · A rune is Go’s predeclared alias for int32 that represents a Unicode code point.
- Unicodeproduced by · Unicode is a standard that assigns code points and properties to characters and defines rules for representing and processing text across writing systems.
- ordproduced by · ord is a function or method that returns the integer character code or Unicode code point associated with a character.
- code unitused by · A code unit is a fixed-size numeric unit used by a character encoding to represent text, such as a 16-bit unit in UTF-16.
- surrogate pairimplemented by · A surrogate pair is two UTF-16 code units that together represent one Unicode code point outside the Basic Multilingual Plane.
- sorting algorithmmeasured by · A sorting algorithm is a procedure that rearranges elements of a collection into an order determined by an ordering criterion.
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