1.5.1 ASCII (American Standard Code for Information Interchange)

Definition

ASCII is a character encoding standard that represents text in computers and communication systems using numeric codes. It assigns a unique number (from 0 to 127) to each character, including letters, digits, punctuation marks, and control characters.

Key Features of ASCII

1. 7-bit Encoding:
   ASCII uses 7 bits to represent a character, allowing it to represent a total of 128 characters (2^7 = 128).

2. Character Set:
   The first 32 codes (0-31) are control characters like line breaks and tabs, and the rest (32-127) represent printable characters like:

   • A-Z (uppercase letters)
   • a-z (lowercase letters)
   • 0-9 (digits)
   • Punctuation marks (., !, ?, etc.)

3. Standard for English Characters:
   ASCII was designed primarily for English and uses the English alphabet.

Example of ASCII Codes

• A = 65
• a = 97
• 0 = 48
• Space = 32
• # = 35

Limitations of ASCII

1. Limited Characters:
   ASCII only supports 128 characters, which is insufficient for representing other languages and special symbols.

2. English-Centric:
   ASCII was originally designed for English, limiting its global application.

1.5.2 Unicode

Definition

Unicode is a universal character encoding standard that aims to represent characters from all the world’s writing systems, providing a unique code for every character, no matter the platform, program, or language. It was created to overcome the limitations of ASCII and other character encoding systems.

Key Features of Unicode

1. Universal Coverage:
   Unicode supports over 1.1 million characters and includes symbols, characters from all languages, emojis, and many more.

2. Variable-Length Encoding:
   Unicode supports different encoding forms:

   • UTF-8: Uses 1 to 4 bytes per character. It is the most widely used Unicode encoding on the web.
   • UTF-16: Uses 2 or 4 bytes per character. Commonly used in Windows and Java.
   • UTF-32: Uses 4 bytes for every character, providing a fixed length but wasting memory for smaller characters.

3. Global Language Support:
   Unicode covers characters from virtually all languages, including:

   • Latin, Greek, Cyrillic alphabets
   • Chinese, Japanese, Korean characters
   • Arabic, Hebrew, and many others
   • Special symbols and emojis.

4. Code Points:
   Each character in Unicode is assigned a unique code point. For example, the code point for “A” is U+0041, for “日” (Chinese character for “day”) is U+65E5, and for the smiley face emoji 😀 is U+1F600.

Example of Unicode Characters

• A = U+0041 (Hexadecimal)
• a = U+0061
• 日 = U+65E5
• 😀 = U+1F600

Advantages of Unicode

1. Universal Support:
   Unicode can represent characters from all languages, making it ideal for internationalization and multilingual applications.

2. Consistency:
   Unicode ensures that characters are represented consistently across different platforms and software, eliminating compatibility issues.

3. Flexibility:
   Unicode allows for both simple and complex characters (e.g., emojis, mathematical symbols, and historical scripts).

Comparison Between ASCII and Unicode

Conclusion

• ASCII is a simpler, older encoding standard focused on English text and basic control characters. It has a limited character set, making it less suitable for international or multi-language systems.
• Unicode, on the other hand, is a much more advanced and comprehensive standard that allows for the representation of virtually every character in any language, including special symbols and emojis, enabling global communication and software compatibility.

Understanding both standards is essential for modern computing, particularly for software development, web design, and database management, where the need for cross-language and cross-platform compatibility is crucial.