- In full:
- American Standard Code for Information Interchange
- Related Topics:
- ASCII art
- extended ASCII
- coding system
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What is ASCII?
ASCII (American Standard Code for Information Interchange) is a standard data-encoding format that enables electronic communication between computers by assigning numeric values to characters, numerals, punctuation marks, and more.
Before ASCII, different computers couldn't communicate effectively because each manufacturer had its own character sets. In 1961, Bob Bemer of IBM proposed a common computer code to ANSI, leading to ASCII's approval as the American standard in 1963.
ASCII was initially created for teleprinters but became widely used in personal computers like IBM's first PC in 1981. It uses seven-digit binary numbers to represent 128 different characters. Extended ASCII uses an eight-bit system, increasing the number of representable characters to 256, which allows special characters and other languages to be represented.
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Why was ASCII created?
ASCII (American Standard Code for Information Interchange) was created to establish a standard data-encoding format for electronic communication between computers. Before ASCII, different computer manufacturers used their own methods to represent characters, causing incompatibility issues. In 1961, Bob Bemer of IBM proposed a common computer code to ANSI (American National Standards Institute), and in 1963, ASCII was approved as the American standard. In 1968, U.S. President Lyndon B. Johnson mandated that all new computers purchased by the U.S. government should be ASCII-compatible. Today, Unicode is more common, but it incorporates ASCII as its first 128 code combinations.
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How does ASCII represent letters and numbers?
ASCII is a standard data-encoding format used for electronic communication between computers. It assigns numeric values to letters, numerals, punctuation marks, and other characters.
ASCII uses seven-digit binary numbers (0s and 1s) to represent 128 different characters. For example, the binary sequence 1010000 represents an uppercase P, while 1110000 represents a lowercase p.
Because digital computers use bytes (eight-digit groups), ASCII is commonly embedded in an eight-bit field. This increases the number of characters ASCII can represent to 256 and ensures that all special characters, as well as characters from other languages, can be represented. Learn more about ASCII.
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What is the difference between uppercase and lowercase in ASCII?
In ASCII, both uppercase and lowercase letters are represented using distinct binary sequences. ASCII uses seven-digit binary numbers, and with 128 possible combinations, it can represent 128 different characters. For example, the binary sequence
1010000represents an uppercase P, while the sequence1110000represents a lowercase p.Extended ASCII uses an eight-bit system, increasing the number of characters to 256, which allows for the representation of special characters and characters from other languages.
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How is ASCII used in computers and communication devices?
ASCII (American Standard Code for Information Interchange) is a standard data-encoding format that enables electronic communication between computers by assigning numeric values to characters.
Originally developed for teleprinters, ASCII found widespread use in personal computers, starting with IBM's first PC in 1981. It employs seven-digit binary numbers to represent 128 different characters. Digital computers use an eight-bit code (a byte), embedding ASCII and increasing the number of characters to 256, including special symbols and characters from other languages. Extended ASCII uses 32 code combinations for machine and control commands like "backspace".
ASCII art, which uses ASCII characters to produce images, is commonly found in online chats, emails, and as signatures in messages, showcasing its versatility in computer-mediated communication.
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What are some limitations of ASCII and how have newer systems improved on it?
ASCII, a standard data-encoding format for electronic communication between computers, assigns numeric values to letters, numerals, punctuation marks, and other characters.
One limitation of ASCII is that even extended ASCII does not have enough code combinations to support all written languages, as it can only represent 256 different characters. Asian languages, for example, require thousands of characters.
Newer systems like Unicode and UCS (Universal Coded Character Set) can support all the principal written languages. Unicode, introduced in 1991, is backward-compatible with ASCII, incorporating it as its first 128 code combinations, while also representing many characters that ASCII cannot. Unicode has become the most common character-encoding system on the World Wide Web. With Unicode, the unique number provided for each character remains the same on any system that supports Unicode.
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ASCII, a standard data-encoding format for electronic communication between computers. ASCII assigns standard numeric values to letters, numerals, punctuation marks, and other characters used in computers.
Before ASCII was developed, different makes and models of computers could not communicate with one another. Each computer manufacturer represented alphabets, numerals, and other characters in its own way. IBM (International Business Machines Corporation) alone used nine different character sets. In 1961 Bob Bemer of IBM submitted a proposal to the American National Standards Institute (ANSI) for a common computer code. The X3.4 committee, with representation from key computer manufacturers of the day, was formed to work on the new code. On June 17, 1963, ASCII was approved as the American standard. However, it did not gain wide acceptance, mainly because IBM chose to use EBCDIC (Extended Binary Coded Decimal Interchange Code) in its OS/360 series of computers released in 1964. Nevertheless, ASCII underwent further development, and revisions were issued in 1965 and 1967. On March 11, 1968, U.S. Pres. Lyndon B. Johnson mandated that ASCII be termed a federal standard to minimize incompatibility across federal computer and telecommunications systems. Furthermore, he mandated that all new computers and related equipment purchased by the U.S. government from July 1, 1969, onward should be ASCII-compatible. The code was revised again in 1968, 1977, and 1986.
ASCII was originally developed for teleprinters, or teletypewriters, but it eventually found wide application in personal computers (PCs), beginning with IBM’s first PC, in 1981. ASCII uses seven-digit binary numbers—i.e., numbers consisting of various sequences of 0’s and 1’s. Since there are 128 different possible combinations of seven 0’s and 1’s, the code can represent 128 different characters. The binary sequence 1010000, for example, represents an uppercase P, while the sequence 1110000 represents a lowercase p.
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Digital computers use a binary code that is arranged in groups of eight, rather than seven, digits, or bits; each such eight-bit group is called a byte. Consequently, ASCII is commonly embedded in an eight-bit field, which consists of the seven information bits and a parity bit that is used for error checking or for representing special symbols. This eight-bit system increases the number of characters ASCII can represent to 256, and it ensures that all special characters, as well as characters from other languages, can be represented. Extended ASCII, as the eight-bit code is known, was introduced by IBM in 1981 for use in its first PC, and it soon became the industry standard for personal computers. In extended ASCII, 32 code combinations are used for machine and control commands, such as “start of text,” “carriage return,” and “form feed.” Control commands do not represent printable information, but rather they help control devices, such as printers, that may use ASCII. For example, the binary sequence 00001000 represents “backspace.” Another group of 32 combinations is used for numerals and various punctuation marks, another for uppercase letters and a few other punctuation marks, and yet another for lowercase letters.
However, even extended ASCII does not include enough code combinations to support all written languages. Asian languages, for instance, require thousands of characters. This limitation gave rise to new encoding standards—Unicode and UCS (Universal Coded Character Set)—that can support all the principal written languages. Because it incorporates ASCII as its first 128 code combinations, Unicode (specifically UTF-8) is backward-compatible with ASCII while also representing many characters that ASCII cannot. Unicode, which was introduced in 1991, saw its usage jump sharply in the first decade of the 21st century, and it became the most common character-encoding system on the World Wide Web.