The ASCII standard maps 128 characters — 33 control codes and 95 printable symbols — to integers 0–127, forming the foundation of nearly all modern text encoding including UTF-8. This reference table shows every character alongside its decimal, hexadecimal, octal, binary, and HTML entity representations for quick lookup during debugging, encoding work, or learning.
Characters 0–31 and 127 are non-printable control codes: tab (9), line feed (10), carriage return (13), escape (27), and others inherited from teletype machines. Characters 32–126 are printable: space, digits 0–9 (48–57), uppercase A–Z (65–90), lowercase a–z (97–122), and punctuation. Knowing these ranges helps when parsing binary formats, writing regex character classes, or debugging encoding issues between systems.
ASCII covers 128 characters; Unicode covers over 140,000. UTF-8 is backward-compatible with ASCII — characters 0–127 encode identically. Unicode extends ASCII rather than replacing it.
ASCII was designed in 1963 for teletype machines. Values 0–31 were reserved for control commands. Character 32 was the first printable slot and was assigned to the space character.
DEL (127) was originally used to erase characters on paper tape by punching all holes. ESC (27) begins escape sequences in terminals — for example, ESC[1m is the ANSI bold sequence.
Most control characters have keyboard shortcuts: Ctrl+C is ETX (3), Ctrl+D is EOT (4), Ctrl+J is LF (10), Ctrl+M is CR (13). The numeric relationship is: Ctrl+A = 1, Ctrl+B = 2, etc.
See also the Hex to Text converter and Binary to Text for encoding lookups.