ASCII

ASCII (American Standard Code for Information Interchange) is a 7-bit character encoding standard that defines 128 characters (0-127), covering English letters, digits, punctuation, and control characters.

Purpose

It provided early computers and communication equipment with a unified character standard so that text could be interchanged between devices from different vendors.

Mechanism

Each character is represented in 7 bits, usually stored in 1 byte (the high-order bit is 0 or used for parity). Codes 0-31 and 127 are control characters; 32-126 are printable. Modern encodings such as UTF-8 are supersets of ASCII.

Use cases

Protocol keywords and HTTP headers
Default character set for source code and configuration files
Serial and embedded communication
Domain name labels in DNS records

Examples

Input
```
A
```
Output
```
65
```
The ASCII code of uppercase A is 65

Common errors

Mistaking extended ASCII (128-255) for standard ASCII: Standardize on UTF-8 encoding

Related terms

Unicode is the international character encoding standard that assigns a unique code point (U+0000 through U+10FFFF) to every character of nearly all the world's writing systems, with a codespace of 1,114,112 code points.

UTF-8 is Unicode's variable-length encoding form, using 1 to 4 bytes per code point; it is fully backward compatible with ASCII and is the de facto standard for the web and modern systems.

A character set (charset) is the mapping table from characters to code points; together with an encoding form (such as UTF-8) it determines how text becomes a byte stream.

A code point is the numeric value the Unicode standard assigns to each character (U+0000 to U+10FFFF), the character's position number in the codespace.

Related tools

Complete ASCII reference table (0-127) with decimal, hex, octal, binary, and character. Free, private, and 100% client-side.

Charset Reference

Reference table of character encodings. Free, private, 100% client-side.

Encoding Detector

Check text encoding: ASCII subset, UTF-8 BOM, and non-ASCII characters. Text input is always re-encoded as UTF-8, so legacy encodings (GBK/Big5/Shift-JIS) cannot be distinguished — the tool honestly reports the UTF-8 byte form. Free, private, 100% client-side.

References