What is ASCII?

ASCII (American Standard Code for Information Interchange) is a character encoding standard that represents text in computers and other devices. Originally developed in the 1960s, ASCII uses 7 bits to represent 128 characters (0-127), including letters, digits, punctuation marks, and control characters.

Extended ASCII uses 8 bits to represent 256 characters (0-255), adding 128 additional characters for special symbols, accented letters, and other international characters. The Extended ASCII set varies by encoding (like ISO-8859-1 or Windows-1252), but this table shows the standard Extended ASCII character set.

Each ASCII character has multiple representations:

• Decimal (0-255): The standard numeric representation, most commonly used in programming
• Hexadecimal (0x00-0xFF): Base-16 representation, commonly used in memory addresses and binary data
• Octal (000-377): Base-8 representation, less common but still used in some systems
• Binary (0b00000000-0b11111111): Base-2 representation, showing the actual bit pattern
• HTML Entity: The HTML representation for use in web pages (e.g., A for 'A')
• Character: The visual representation of the character itself

ASCII Character Sets

Common Use Cases

• Character Encoding: Understanding how characters are represented in different number systems (decimal, hex, octal, binary) is essential for working with character encodings, file formats, and data processing.
• String Manipulation: Converting between character codes and characters is common in programming. Functions like charCodeAt() and fromCharCode() in JavaScript use ASCII values.
• Data Validation: Checking if characters fall within specific ranges (e.g., alphanumeric: 48-57, 65-90, 97-122) is useful for input validation and data cleaning.
• HTML Development: HTML entities allow you to display special characters that might conflict with HTML syntax or aren't easily typed on keyboards.
• Debugging: When debugging character-related issues, knowing the exact ASCII value helps identify problems with encoding, special characters, or control characters.
• File Processing: Binary file formats often use specific ASCII values as delimiters, markers, or control codes. Understanding these values is crucial for parsing files correctly.
• Network Protocols: Many network protocols use ASCII control characters (e.g., CRLF for line endings) or specific ASCII values for protocol-specific purposes.
• Cryptography: Character encoding knowledge is important in cryptography, where characters are often converted to numeric values for mathematical operations.

Frequently Asked Questions