ASCII
Overview
ASCII (American Standard Code for Information Interchange) is a character encoding standard used to represent text in computers and other devices that use text. It is a 7-bit character set containing 128 characters. It contains the numbers from 0-9, the upper and lower case English letters from A to Z, and some special characters. The ASCII standard allows ASCII-only text files to be freely interchanged and readable on Unix, Macintosh, Microsoft Windows, DOS, and other systems.
History
ASCII was developed from telegraph code. Its first commercial use was as a seven-bit teleprinter code promoted by Bell data services. Work on the ASCII standard began on October 6, 1960, with the first meeting of the American Standards Association's (ASA) X3.2 subcommittee. The first edition of the standard was published in 1963. The ASA became the United States of America Standards Institute (USASI) and ultimately the American National Standards Institute (ANSI).
Character Encoding
Character encoding is a method of converting bytes into characters. To understand how ASCII is used to encode text, it is helpful to understand a bit about how computers represent characters in memory and on disk. A computer system typically uses a byte of memory to store a character. A byte is a small chunk of data that is addressable in memory. A byte is made up of 8 bits, and each bit can be in one of two states, leading to a total of 256 (2^8) possible combinations. ASCII uses only 7 bits, so it can represent 128 (2^7) characters.
ASCII Table
The ASCII table contains letters, numbers, control characters, and other symbols. Each character is assigned a unique 7-bit code. ASCII can be divided into two parts: the ASCII printable characters (from values 32 to 126) and the ASCII control characters (from values 0 to 31 and 127). Control characters are used to control some peripheral devices such as printers.
ASCII and Programming
ASCII plays a crucial role in programming. High-level languages, like Java, C#, Python, and others, use ASCII for text manipulation. For example, the lowercase "a" is represented by 97 in ASCII. In programming languages, we can use the ASCII values to handle text in various ways.
ASCII and Communication Protocols
ASCII is also used in communications protocols. For example, the HTTP protocol uses ASCII to format requests and responses. In addition, many protocols use ASCII encoding for sending and receiving messages. For instance, the SMTP protocol for sending email also uses ASCII.
ASCII Art
ASCII art is a graphic design technique that uses printable characters from the ASCII standard to create images and designs. ASCII art can be created with any text editor, and is often used in online communications to create shapes and symbols.
Limitations and Alternatives
While ASCII is widely used, it has its limitations. It can only represent 128 characters, which is not enough for languages other than English. Alternatives to ASCII have been developed to accommodate these languages. Unicode is an example of such an alternative. Unicode uses more bits to represent each character, allowing it to represent characters from many different languages.