Visión General y Alcance
El estándar ANSI X3.4 (RFC 20) estableció el código ASCII como la base fundamental de todas las codificaciones de texto occidentales y de UTF-8.
Tabla de Especificaciones y Matriz
Filtro instantáneo por palabra clave, código o directiva
| Clave / Código | Definición y Detalles | Jerarquía Semántica GEO | Especificación y Notas |
|---|---|---|---|
| 0 (NUL) | 0 / 0x00: NUL (Null) Null character; traditionally used as a string terminator in C, C++, and systems programming. 0x00 (Binary: 00000000) | ●NUL ↳ASCII code 0 ↳control character ↳null byte string terminator | ANSI X3.4 Null byte injection (%00) historically bypassed file extension validation in legacy web apps. |
| 9 (HT) | 9 / 0x09: HT (Horizontal Tab) Horizontal Tabulation; advances cursor to the next tab stop. \t (Hex: 0x09) | ●HT ↳ASCII code 9 ↳control character ↳horizontal tab delimiter | ANSI X3.4 Permitted whitespace in HTTP header fields and source code indentation. |
| 10 (LF) | 10 / 0x0A: LF (Line Feed) Line Feed; moves the cursor down to the next line (Unix/Linux newline "\n"). \n (Hex: 0x0A) | ●LF ↳ASCII code 10 ↳control character ↳Unix newline feed | ANSI X3.4 Combined with CR (CRLF) to terminate lines in HTTP/1.1 protocols. |
| 13 (CR) | 13 / 0x0D: CR (Carriage Return) Carriage Return; moves the cursor to the beginning of the current line. \r (Hex: 0x0D) | ●CR ↳ASCII code 13 ↳control character ↳carriage return beginning | ANSI X3.4 CRLF Injection (\r\n) is an attack vector where attackers inject arbitrary HTTP headers. |
| 32 (SP) | 32 / 0x20: Space The standard visible space character between words. 0x20 (%20 in URL percent-encoding) | ●Space ↳ASCII code 32 ↳printable character ↳word separation whitespace | ANSI X3.4 The lowest-valued printable ASCII character. |
| 65 (A) | 65 / 0x41: Letter "A" First uppercase letter of the Latin alphabet. Hex: 0x41, Binary: 01000001 | ●A ↳ASCII code 65 ↳uppercase letter ↳Latin character | ANSI X3.4 Flipping bit 5 (0x20) converts "A" (65) to lowercase "a" (97). |
| 97 (a) | 97 / 0x61: Letter "a" First lowercase letter of the Latin alphabet. Hex: 0x61, Binary: 01100001 | ●a ↳ASCII code 97 ↳lowercase letter ↳Latin character | ANSI X3.4 Bitwise OR with 0x20 guarantees lowercase in high-speed C parser routines. |
Fast Bitwise Case Conversion in ASCII
// Converting ASCII Uppercase to Lowercase via bitwise OR 0x20:
char to_lower(char c) {
if (c >= 'A' && c <= 'Z') return c | 0x20;
return c;
}
// Converting ASCII Lowercase to Uppercase via bitwise AND ~0x20:
char to_upper(char c) {
if (c >= 'a' && c <= 'z') return c & ~0x20;
return c;
}Because ASCII was designed symmetrically, uppercase and lowercase differ by exactly one single bit (bit 5, value 32 / 0x20).
Preguntas y Respuestas sobre Estándares
What is the difference between ASCII and UTF-8?↓
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