What are the differences between ASCII, ISO 8859, and Unicode?

ASCII is a seven-bit encoding technique which assigns a number to each of the 128 characters used most frequently in American English. This allows most computers to record and display basic text. ASCII does not include symbols frequently used in other countries, such as the British pound symbol or the German umlaut. ASCII is understood by almost all email and communications software.

ISO 8859 is an eight-bit extension to ASCII developed by ISO (the International Organization for Standardization). ISO 8859 includes the 128 ASCII characters along with an additional 128 characters, such as the British pound symbol and the American cent symbol. Several variations of the ISO 8859 standard exist for different language families:

• Latin-1 (Western European languages)
  
  
• Latin-2 (Non-Cyrillic Central and Eastern European languages)
  
  
• Latin-3 (Southern European languages and Esperanto)
  
  
• Latin-5 (Turkish)
  
  
• Latin-6 (Northern European and Baltic languages)
  
  
• 8859-5 (Cyrillic)
  
  
• 8859-6 (Arabic)
  
  
• 8859-7 (Greek)
  
  
• 8859-8 (Hebrew)

Not all email or communications software can understand ISO-8859 character sets.

Unicode is an attempt by ISO and the Unicode Consortium to develop a coding system for electronic text that includes every written alphabet in existence. Unicode uses 8-, 16-, or 32-bit characters depending on the specific representation, so Unicode documents often require up to twice as much disk space as ASCII or Latin-1 documents. The first 256 characters of Unicode are identical to Latin-1. Not all email or communications software can understand the Unicode character set.

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