ASCII

Byte Structure

When to Use ASCII

Sample Characters in ASCII

The table below shows how a selection of characters are represented in ASCII. Bytes are shown in hexadecimal. Characters marked "not supported" cannot be encoded in ASCII and would need to be replaced or transliterated when converting from Unicode.

Working with ASCII in Code

Every major language has built-in support for encoding conversion. The examples below show how to encode a string to ASCII bytes and decode it back to a Unicode string. Always specify the encoding explicitly — never rely on system defaults, which vary by OS and locale.

# Encode a string to ascii bytes
text = "Hello, 世界"
encoded = text.encode("US-ASCII")

# Decode bytes back to a string
decoded = encoded.decode("US-ASCII")

// Convert to ascii
$bytes = mb_convert_encoding(
    "Hello, 世界",
    "US-ASCII",
    "UTF-8"
);

// Convert back to UTF-8
$text = mb_convert_encoding(
    $bytes,
    "UTF-8",
    "US-ASCII"
);

// Encode to US-ASCII bytes
const encoder = new TextEncoder(); // UTF-8
const bytes = encoder.encode("Hello, 世界");

// Decode bytes
const decoder = new TextDecoder("US-ASCII");
const text = decoder.decode(bytes);

-- Create a database with ASCII
CREATE DATABASE mydb
  ENCODING 'US-ASCII'
  LC_COLLATE 'en_US.UTF-8';

-- Check database encoding
SELECT pg_encoding_to_char(encoding)
FROM pg_database
WHERE datname = current_database();

Compare with Other Encodings

See how ASCII differs from other encodings — which characters each supports and how the byte representations compare.