What is ASCII?

ASCII (pronounced "ask-ee") stands for American Standard Code for Information Interchange. It's a character encoding standard that assigns numeric values (0-127) to letters, numbers, punctuation marks, and control characters.

ASCII is the foundation of text representation in computers and has been the backbone of digital communication since the 1960s.

Quick Facts

Full Name: American Standard Code for Information Interchange
Pronunciation: ASK-ee
Character Range: 0-127 (7-bit encoding)
Extended Range: 128-255 (8-bit, non-standard)
First Published: 1963
Current Standard: ANSI X3.4-1986, RFC 20
Use Case: Text representation, data transmission, programming

ASCII Character Ranges

0-31: Control Characters

Non-printable characters used for text control and communication.

NULL (0): Null character
LF (10): Line feed (newline)
CR (13): Carriage return
ESC (27): Escape
DEL (127): Delete

32-126: Printable Characters

Standard visible characters including letters, numbers, and symbols.

32-47: Space and punctuation
48-57: Digits 0-9
65-90: Uppercase A-Z
97-122: Lowercase a-z
Special chars: !@#$%^&*() etc.

128-255: Extended ASCII

Non-standard extended characters (varies by implementation).

International characters
Special symbols
Box-drawing characters
Not part of standard ASCII
Implementation-dependent

History of ASCII

1960: Work begins on ASCII by the American Standards Association (ASA).

1963: First ASCII standard published (ASA X3.4-1963).

1967: Major revision adds lowercase letters and refinements.

1986: Last major update (ANSI X3.4-1986), still in use today.

1990s-Present: ASCII becomes foundation for Unicode (UTF-8), which maintains backward compatibility with ASCII.

How ASCII Works

ASCII uses 7 bits to represent 128 different characters. Each character is assigned a unique decimal number from 0 to 127, which can also be expressed in binary, octal, or hexadecimal.

Example: The letter 'A'
Decimal: 65 | Binary: 01000001 | Octal: 101 | Hex: 41

Common ASCII Values

Character	Decimal	Hex	Description
Space	32	0x20	Space character
0	48	0x30	Digit zero
A	65	0x41	Uppercase A
a	97	0x61	Lowercase a
LF	10	0x0A	Line feed (newline)

ASCII in Programming

ASCII is fundamental to programming. Most programming languages provide functions to convert between characters and their ASCII values.

Examples in Different Languages

// JavaScript
'A'.charCodeAt(0);  // Returns: 65
String.fromCharCode(65);  // Returns: 'A'
    

# Python
ord('A')  # Returns: 65
chr(65)  # Returns: 'A'
    

// C/C++
char c = 'A';
int ascii = (int)c;  // Returns: 65
    

ASCII vs. Unicode

Feature	ASCII	Unicode (UTF-8)
Characters	128 (7-bit)	1,114,112+ characters
Languages	English only	All world languages
Size	1 byte per character	1-4 bytes per character
Compatibility	Limited to Latin alphabet	Backward compatible with ASCII
Emojis	Not supported	Fully supported 😀

        Important: UTF-8 (the most common Unicode encoding) is designed to be backward compatible with ASCII. The first 128 characters of UTF-8 are identical to ASCII, meaning any valid ASCII text is also valid UTF-8.
    

Practical Applications

Text Files: Plain text files (.txt) typically use ASCII or UTF-8 encoding
Programming: Source code files are often ASCII or ASCII-compatible
Data Transmission: Email, HTTP, and many protocols use ASCII
Terminal/CLI: Command-line interfaces rely on ASCII characters
CSV Files: Comma-separated values typically use ASCII
Configuration Files: Many config files use ASCII encoding

Fun Facts About ASCII

The difference between uppercase and lowercase letters in ASCII is always 32 (e.g., 'A' = 65, 'a' = 97)
This makes case conversion in ASCII very efficient with bitwise operations
The '@' symbol was almost removed from ASCII but was kept due to its use in email addresses
ASCII was designed with a focus on telecommunications and early computer systems
The layout of ASCII was designed to make sorting and comparison operations efficient
Control characters (0-31) were designed for teletype machines and early terminals

ASCII Art

ASCII art is a creative use of ASCII characters to create images and designs. It was particularly popular in the early days of computing when graphical displays were limited.

  ___   _____ _____ ___ ___
 / _ \ / ____/ ____|_ _|_ _|
| |_| | (___| |     | | | |
|  _  |\___ \ |     | | | |
| | | |____) | |___ | |_| |_
|_| |_|_____/ \____|___|___|

Visual Reference

(Image Credit: WikiMedia ASCII-Table.svg: ZZT32derivative work: LanoxxthShaddow [Public domain])

Related Standards

Extended ASCII: 8-bit extensions (128-255) - not standardized, varies by code page
ISO 8859-1 (Latin-1): Western European extension of ASCII
UTF-8: Variable-width Unicode encoding, ASCII-compatible
UTF-16: 16-bit Unicode encoding
UTF-32: 32-bit Unicode encoding

ASCII INFO