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(also American Standard for Information Interchange)

ASCII definition

ASCII (short for “American Standard Code for Information Interchange”) is a character encoding standard developed in the early 1960s. ASCII uses numeric codes to represent characters, with unique values for 128 alphabetic, numeric or special characters in the standard set.

See also: character set

How ASCII works

Each ASCII character is represented by a 7-bit binary number, with the most significant bit (the eighth bit) often set to zero. ASCII provides a specific mapping of characters to numerical values. For example, the uppercase letter 'A' is represented by the decimal value 65 (or “01000001” in binary code), while the lowercase 'a' is represented by 97 (or “01100001” in binary).

Although standard ASCII consists of 128 values, only 95 (values 32 to 126) represent printable characters like letters or digits that are used in written language and programming. The first 32 characters (values 0 to 31) are control characters — they are typically not printable, instead being used for controlling devices (like printers) or signaling specific actions (like carriage return and line feed).

Extended ASCII

The 128 characters used in standard ASCII cover all the symbols needed for a conversation in English, but they are lacking when it comes to other languages. Extended ASCII remedies this by making use of the final 8th bit, allowing for a total of 256 characters.

However, while extended ASCII lets users type accented letters, special symbols, and characters specific to different languages, its use is not standardized between different systems and may result in different symbols being displayed between two users.