ASCII テーブル 完了 リファレンス

Control Characters (0-31)

The first 32 ASCII code points are non-printable control characters originally designed for teletype machines. Many are obsolete in modern usage, but several remain essential in terminals and protocols. For example, LF (line feed) and CR (carriage return) still delimit text lines, while ESC introduces escape sequences. NUL serves as a string terminator in C-style APIs. Transmitting most control characters over text protocols can cause unintended side effects.

NUL

Null character, value 0, string terminator in C

0x00

LF

Line feed, value 10, newline in Unix

0x0A

CR

Carriage return, value 13, newline in classic Mac

0x0D

ESC

Escape, value 27, introduces escape sequences

0x1B

DEL

Delete, value 127, rubout in paper tape

0x7F

Printable Characters (32-126)

Code points 32 through 126 are the printable ASCII characters, including the space at 32 and the tilde at 126. Digits 0-9 occupy the contiguous range 48-57, uppercase letters 65-90, and lowercase letters 97-122. Converting between cases is a single bit flip because the two ranges differ only by bit 5. This regularity enables fast, branchless case conversion in performance-critical code.

Extended ASCII

Code points 128-255 are not part of standard ASCII and are interpreted differently by each extended code page. Latin-1 (ISO-8859-1) fills them with Western European accented letters, while CP437 uses them for box-drawing glyphs. UTF-8 reuses the 128-255 range as continuation bytes, making raw high bytes ambiguous without an explicit encoding declaration. Always specify the encoding when handling bytes above 127.