Latin Capital Letter D
Occupying the fourth position in the Latin alphabet, uppercase 'D' is the fourth of the six hexadecimal letter-digits, representing the value 13. It sits at ASCII code point 68 (0x44), exactly 32 below its lowercase counterpart 'd' at 100 (0x64) — the single-bit case offset (bit 5) shared by all ASCII A–Z / a–z pairs. In English, uppercase 'D' enjoys steady visibility at sentence boundaries through high-frequency words like 'Do', 'Did', and 'Don't', and carries heavy symbolic weight in grading systems, Roman numerals (500), and musical key signatures.
Technical Details
Code Example
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// Check if character is valid hex digitchar c = 'D';bool isHex = (c >= '0' && c <= '9') || (c >= 'A' && c <= 'F');// isHex == true
Common Usage
Hexadecimal digit: Uppercase 'D' represents 13 in hex, the fourth of the six letter-digits in the A–F range. It appears in common byte patterns — 0x0D is the ASCII carriage return (CR), making it half of the Windows-style \r\n line ending. C-family printf-style formatting with %X produces uppercase hex output including 'D'.
Printf format specifier overlap: In C-family printf-style formatting, lowercase '%d' is the standard signed decimal integer specifier, one of the most frequently typed format tokens in systems programming. Uppercase 'D' itself formerly served as a long-integer specifier ('%D') in some older Unix implementations, but this usage is now obsolete and non-portable — modern code uses '%ld' instead.
Typographic structure: Uppercase 'D' consists of a vertical stem and a single bowl curving from top to bottom, giving it a half-enclosed counter. Distinguishing it from 'B' (two bowls), 'P' (upper bowl only), and 'O' (fully enclosed) is a key task in typeface legibility testing. In monospaced fonts, the bowl's curvature is often flattened to fit the fixed-width cell, a compromise that can reduce readability at small sizes.
Diacritical variants: Uppercase Đ (stroke) is a distinct letter in Croatian, Vietnamese, and Sami languages, with its own alphabetical position and phonetic value. Ď (caron) appears in Czech and Slovak, representing a palatal stop /ɟ/. Ḍ (dot below) is used in IAST and other transliteration schemes for Indic and Semitic languages, while Ð (eth) — though historically derived from 'D' — functions as a separate letter entirely in Icelandic and Faroese.
Hexadecimal digit: Uppercase 'D' represents 13 in hex, the fourth of the six letter-digits in the A–F range. It appears in common byte patterns — 0x0D is the ASCII carriage return (CR), making it half of the Windows-style \r\n line ending. C-family printf-style formatting with %X produces uppercase hex output including 'D'.
Printf format specifier overlap: In C-family printf-style formatting, lowercase '%d' is the standard signed decimal integer specifier, one of the most frequently typed format tokens in systems programming. Uppercase 'D' itself formerly served as a long-integer specifier ('%D') in some older Unix implementations, but this usage is now obsolete and non-portable — modern code uses '%ld' instead.
Typographic structure: Uppercase 'D' consists of a vertical stem and a single bowl curving from top to bottom, giving it a half-enclosed counter. Distinguishing it from 'B' (two bowls), 'P' (upper bowl only), and 'O' (fully enclosed) is a key task in typeface legibility testing. In monospaced fonts, the bowl's curvature is often flattened to fit the fixed-width cell, a compromise that can reduce readability at small sizes.
Diacritical variants: Uppercase Đ (stroke) is a distinct letter in Croatian, Vietnamese, and Sami languages, with its own alphabetical position and phonetic value. Ď (caron) appears in Czech and Slovak, representing a palatal stop /ɟ/. Ḍ (dot below) is used in IAST and other transliteration schemes for Indic and Semitic languages, while Ð (eth) — though historically derived from 'D' — functions as a separate letter entirely in Icelandic and Faroese.