ASCII stands for American Standard Code for Information Interchange. It was defined in 1963 and assigns a number between 0 and 127 to every English letter, digit, punctuation mark, and control character. Despite its age, ASCII is the foundation of nearly every text encoding system in use today, including UTF-8, the dominant encoding on the web.
What ASCII Covers
The ASCII table covers 128 characters. Characters 0 through 31 are control characters: non-printing signals like newline (10), carriage return (13), tab (9), and null (0). Characters 32 through 126 are printable: the space, all punctuation marks, digits 0 through 9, uppercase letters A through Z, and lowercase letters a through z. Character 127 is the delete control character.
Why Developers Need ASCII Codes
String processing in programming often relies on character codes rather than the character itself. Checking whether a character is a digit by comparing its code to the range 48 to 57 (the ASCII codes for 0 through 9) is a pattern found in every programming language.
ASCII codes also appear when working with binary protocols, serial communication, terminal emulators, and text encodings. Understanding that the letter A is ASCII 65 and that lowercase a is ASCII 97 (exactly 32 apart, which is the bit difference between uppercase and lowercase) gives insight into how case conversion and character classification work at the byte level.
Keyboard shortcuts are often described by their ASCII code in system documentation. Control characters are produced by subtracting 64 from the letter's ASCII code (Ctrl+A produces ASCII 1, Ctrl+C produces ASCII 3).
How to Convert Text to ASCII with DevHexLab
Open the ASCII Converter at /tools/encoding/ascii-converter. Type or paste your text. The tool shows each character alongside its decimal, hexadecimal, octal, and binary representations. You can switch the output to show only one format at a time.
Frequently Asked Questions
What is the difference between ASCII and Unicode?
ASCII covers 128 characters. Unicode covers over a million code points representing every writing system in the world. UTF-8 is a variable-length encoding of Unicode that is fully backward compatible with ASCII for the first 128 code points.
What does the null character (ASCII 0) do?
In C-style strings, ASCII 0 marks the end of a string. It is called the null terminator. In network protocols it may be used as a frame boundary.
Understanding ASCII is one of the fundamentals that makes low-level programming and debugging significantly easier.