ASCII vs. Unicode

What's the Difference?

ASCII and Unicode are both character encoding standards used in computing. ASCII, which stands for American Standard Code for Information Interchange, is a 7-bit character set that includes 128 characters, primarily consisting of English alphabets, numbers, and basic symbols. On the other hand, Unicode is a much more comprehensive character encoding system that can represent characters from almost all writing systems in the world. It uses a variable-length encoding scheme, allowing it to represent over 1 million characters. While ASCII is limited to the English language, Unicode supports multiple languages and scripts, making it more versatile and globally applicable.


DefinitionA character encoding standard that represents text in computers and other devices.A universal character encoding standard that supports multiple languages and scripts.
Number of Characters128Over 143,000
Character Size8 bitsVariable (8, 16, 32 bits)
CompatibilityASCII is a subset of Unicode.Unicode includes ASCII as its first 128 characters.
Language SupportPrimarily English and a few other Western languages.Supports a wide range of languages including major scripts and symbols.
UsageCommonly used in older systems and for basic English text.Used in modern systems for multilingual support and internationalization.
RepresentationEach character is represented by a unique 7 or 8-bit binary number.Characters are represented by unique code points ranging from 0 to 10FFFF in hexadecimal.
Backward CompatibilityASCII is backward compatible with older systems.Unicode is backward compatible with ASCII.

Further Detail


When it comes to representing characters in digital form, two widely used character encoding standards are ASCII and Unicode. ASCII, which stands for American Standard Code for Information Interchange, was developed in the 1960s and has been the dominant character encoding scheme for many years. On the other hand, Unicode, introduced in the 1990s, is a more comprehensive and versatile character encoding standard that aims to support characters from all writing systems across the world. In this article, we will explore the attributes of ASCII and Unicode, highlighting their similarities and differences.

Character Set

One of the primary differences between ASCII and Unicode lies in their character sets. ASCII uses a 7-bit character set, which allows for a total of 128 unique characters. These characters include uppercase and lowercase letters, digits, punctuation marks, and a few control characters. On the other hand, Unicode employs a much larger character set, using either 16-bit or 32-bit encoding. The Unicode character set encompasses characters from various scripts, including Latin, Greek, Cyrillic, Arabic, Chinese, Japanese, and many more. This expansive character set enables Unicode to represent a vast range of characters from different languages and writing systems.

Encoding Scheme

ASCII and Unicode also differ in their encoding schemes. ASCII uses a fixed-length encoding scheme, where each character is represented by a 7-bit binary number. This means that ASCII can only represent a limited number of characters, and any character outside the ASCII range cannot be encoded. In contrast, Unicode utilizes variable-length encoding schemes, such as UTF-8, UTF-16, and UTF-32. These encoding schemes allow Unicode to represent a much larger number of characters, including those outside the ASCII range. UTF-8, the most commonly used encoding scheme, uses 8-bit code units and can represent the entire Unicode character set while maintaining backward compatibility with ASCII.


ASCII has excellent compatibility with older systems and software that were designed around the ASCII character set. Since ASCII uses a smaller character set and fixed-length encoding, it is straightforward to convert ASCII-encoded text to Unicode without any loss of information. However, the reverse conversion may result in the loss of non-ASCII characters, as they cannot be represented in ASCII. Unicode, on the other hand, provides backward compatibility with ASCII through its UTF-8 encoding scheme. UTF-8 can represent any ASCII character using a single byte, making it compatible with ASCII-based systems. This compatibility allows Unicode to be seamlessly integrated into existing systems while still supporting a broader range of characters.


One of the significant advantages of Unicode over ASCII is its support for internationalization. ASCII is primarily focused on representing characters used in the English language and lacks support for characters from other languages and scripts. This limitation makes ASCII unsuitable for applications that require multilingual support. Unicode, with its extensive character set, provides a solution to this problem. By including characters from various scripts, Unicode enables software and systems to handle text in multiple languages seamlessly. This internationalization support is crucial in today's globalized world, where communication and information exchange happen across different languages and cultures.


When it comes to efficiency, ASCII has the upper hand over Unicode in terms of storage requirements. Since ASCII uses a fixed-length encoding scheme, each character is represented by a single byte. This simplicity makes ASCII-encoded text more compact and efficient in terms of storage space. On the other hand, Unicode's variable-length encoding schemes, such as UTF-8 and UTF-16, can require multiple bytes to represent certain characters, especially those outside the ASCII range. This increased storage requirement can be a concern in situations where storage space is limited, such as in embedded systems or when transmitting data over low-bandwidth networks.

Platform Support

ASCII enjoys widespread platform support due to its long-standing history and simplicity. Virtually all modern computer systems and programming languages provide built-in support for ASCII encoding. This ubiquity makes ASCII a reliable choice for applications that do not require multilingual support or deal with text primarily in the English language. Unicode, on the other hand, has gained significant adoption over the years and is now widely supported across various platforms and programming languages. Most modern software and operating systems provide native support for Unicode, allowing developers to handle text in different languages and scripts without any major hurdles.


In conclusion, ASCII and Unicode are two character encoding standards with distinct attributes. ASCII, with its limited character set and fixed-length encoding, is suitable for applications that primarily deal with English text and require compatibility with older systems. On the other hand, Unicode's expansive character set, variable-length encoding, and internationalization support make it the preferred choice for applications that need to handle text in multiple languages and scripts. While ASCII remains relevant in certain contexts, Unicode has become the de facto standard for modern software and systems, enabling seamless communication and information exchange across different languages and cultures.

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