ASCII Table

ASCII (American Standard Code for Information Interchange) is a character encoding standard published in 1963 that assigns numeric codes to 128 characters. It includes 33 non-printing control characters (codes 0-31 and 127), the space character (code 32), and 94 printable characters including digits, uppercase and lowercase English letters, and common punctuation and symbols. ASCII forms the foundation of virtually all modern character encoding systems, and its first 128 code points are identical in UTF-8, ISO-8859-1, and Windows-1252.

The standard ASCII table contains exactly 128 characters, numbered 0 through 127 (7 bits). This includes 33 control characters (0-31 plus 127/DEL), 1 space character (32), 10 digits (48-57), 26 uppercase letters (65-90), 26 lowercase letters (97-122), and 32 punctuation/symbol characters. Extended ASCII (codes 128-255) is not part of the original standard and varies by encoding (ISO-8859-1, Windows-1252, etc.).

ASCII defines 128 characters using 7 bits, covering only English letters, digits, and basic symbols. Unicode is a much larger standard that aims to encode every character from every writing system in the world, currently defining over 149,000 characters. The first 128 Unicode code points (U+0000 to U+007F) are identical to ASCII, ensuring backward compatibility. UTF-8, the most common Unicode encoding, uses 1 byte for ASCII characters and 2-4 bytes for other characters.

Control characters (codes 0-31 and 127) are non-printable characters originally designed to control hardware devices like printers and teletypes. Important ones still in use today include: LF (10, Line Feed) for Unix line endings, CR (13, Carriage Return) used with LF for Windows line endings (CR+LF), HT (9, Horizontal Tab) for tab characters, ESC (27, Escape) for terminal escape sequences, NUL (0, Null) as the C string terminator, and BS (8, Backspace). Most others like SOH, STX, ETX, and BEL are primarily relevant in serial communication protocols.

Each ASCII character has equivalent values in different bases. For example, the letter "A" is decimal 65, hexadecimal 0x41, and octal 101. To convert: decimal to hex, divide by 16 and use A-F for remainders 10-15; decimal to octal, divide by 8. This table shows all three representations side by side so you do not need to calculate manually. In programming, hex is commonly used in escape sequences (\x41), octal in older C code (\101), and decimal in general ASCII code references.

The first 32 codes (0-31) are reserved for control characters, and code 32 is the space. Codes 33-47 are punctuation and symbols, and codes 48-57 are the digits 0-9. The uppercase letters start at 65 because the ASCII designers placed control characters, space, symbols, and digits first in the encoding table. A useful property of this arrangement is that the difference between an uppercase letter and its lowercase equivalent is always exactly 32 (e.g., A=65, a=97), which corresponds to a single bit flip (bit 5), making case conversion efficient in binary.

Caret notation represents control characters as ^ followed by another character. It is derived from the fact that control characters are generated by holding Ctrl and pressing a key. ^A (Ctrl+A) is code 1, ^B is code 2, up through ^Z for code 26. ^@ is NUL (code 0), ^[ is ESC (code 27), and ^? is DEL (code 127). This notation is commonly seen in terminal emulators, command-line tools, and text editors like Vim and Nano when displaying non-printable characters.

Use the search bar at the top to search by any attribute. Type a decimal number (e.g., "65") to find that code, a hex value (e.g., "41"), a character (e.g., "A"), or a description keyword (e.g., "Escape" or "Tab"). You can also click the category filter buttons to show only Control characters, Special characters, Digits, Uppercase letters, or Lowercase letters. The result count updates in real time as you type.