Online ASCII Table

 _________________
| | ___________ |o|
| | ___________ | |
| | ___________ | |
| | ___________ | |
| |_____________| |
|     _______     |
|    |       |   ||
| DD |       |   V|
|____|_______|____|

ASCII Overview

ASCII is the abbreviation derived from American Standard Code for Information Interchange. ASCII is a character encoding standard for the electronic communication. With the help of ASCII codes different texts in computers are being represented, as well as telecommunications equipment, and some other devices. ASCII is the essential basis of the most character-encoding schemes of our times, despite the fact that lots of additional characters can be supported by them.

Encoding system conventional name is ASCII. the Internet Assigned Numbers Authority (IANA) uses the modern name US-ASCII. This way it becomes clear that this system was created in the USA. It is also clear that the basis of it are typographical symbols, that are used there in great abundance.

The telegraph code was the predecessor of ASCII, from which it was lately developed. A seven-bit teleprinter code promoted by Bell data services was the first commercial use of ASCII. October 6, 1960 is the day, when the work on the ASCII standard began. Everything started from the first meeting of the American Standards Association's (ASA) (currently the American National Standards Institute or ANSI) Х3.2 subcommittee.

In 1963 the very first edition of the standard was published. In 1967 there was a great revision of it and later on in 1986 ASCII experienced its most recent update. There were some differences from the earlier telegraph codes. The both proposed Bell code and ASCII were ordered just to provide the easier sorting (i.e., alphabetization) of lists, and added features for some other devices than the teleprinters.

ASCII was originally based on the English alphabet. It encodes 128 specified characters into seven-bit integers. The example of it you can see on the ASCII chart above. 95 of the encoded characters can be printed: these are the digits (0, 1, 2, 3, 4, 5, 6, 7, 8, 9), uppercase letters (A to Z), lowercase letters (a to z) and punctuation symbols. 33 non-printing control codes which originated with Teletype machines are included in the original ASCII specification. It is worth mentioning that the most of them are currently outdated. However, some of them are still used everywhere, such as carriage return, line feed and fab codes. They included in the original ASCII specifications.

Let's see the example. The uppercase 'Z' would be represented in the ASCII encoding by binary 01011010 = hexadecimal 5A = decimal 90.

ASCII Table

ASCII History

A committee of the American Standards Association (ASA) was responsible for the creation of the American Standard Code for Information Interchange (ASCII). ASA is also called the X3 committee, by its X3.2 (later X3L2) subcommittee, and later on by the working group of that subcommittee X3.2.4 (now INCITS). The managed to become ASA the United States of America Standards Institute (USASI) and finally the American National Standards Institute (ANSI).

ASCII was published as ASA X3.4-1963 with some other unique characters and control codes filled in. What's more, 28 code positions were left without any particular meaning. They were reserved for the later standardization, and one unassigned control code. At that time specialists couldn't firmly decide whether there should be more control characters rather than the lowercase alphabet. However, this state of uncertainty did not last long: during May 1963 the CCITT Working Party on the New Telegraph Alphabet suggested to assign lowercase characters to sticks 6 and 7. During October the International Organization for Standardization TC 97 SC 2 gave its vote for the incorporation the change into its draft standard. At May 1963 meeting the vote for the change approval to ASCII was given by the X3.2.4 task group. Because of the lowercase letters location in sticks 6 and 7, the characters differed in bit pattern from the upper case by a single bit. This simplified case-insensitive character matching and the construction of keyboards and printers in general.

Some other changes were made by the X3 committee. Among them are some other new characters (the brace and vertical bar characters), renaming some control characters (SOM became start of header (SOH)) and moving or removing others (RU was removed). Later on ASCII was updated as USAS X3.4-1967, then USAS X3.4-1968, ANSI X3.4-1977, and finally, ANSI X3.4-1986.

Revisions of the ASCII standard:

The way how ASCII should be transmitted (least significant bit first), and how it should be recorded on perforated tape was also considered by the X3 committee in the X3.15 standard. They proposed a 9-track standard for magnetic tape, and, what's more, tried to deal with some punched card formats.

ASCII Bit width

ASCII was created based on the earlier teleprinter encoding systems by the X3.2 committee. ASCII can be compared to some other character encodings: it specifies a correspondence between digital bit patterns and character symbols (i.e. graphemes and control characters). This way digital devices can communicate with each other, process, save, and communicate character-oriented information, written language, for example. Before the development of ASCII, the encodings in service included 26 alphabetic characters, 10 numerical digits, and from 11 to 25 unique graphic symbols. International Telegraph Alphabet No. 2 (ITA2) standard of 1924 FIELDATA (1956), and early EBCDIC (1963), more than 64 codes were required for ASCII in order to include all these things and control characters compatible with the International Telegraph and Telephone Consultative Committee (CCITT, from French).

In its turn, the base of the ITA2 was the 5-bit telegraph code Emile Baudot. It was invented in 1870 and patented in 1874.

The possibility of a shift function (like in ITA2) was hotly discussed by the specialists. More than 64 codes could be allowed to be represented by a 6-bit code. In a shifted code, the choices between options for the following character codes are determined by some character codes. The compact encoding is possible here. However, the data transmission becomes not so reliable, because a transmitting shift code error usually makes a great part of the transmission totally unreadable. Taking into consideration these facts, the standards committee decided no to add up the shift function, so ASCII required at least a 7-bit code.

An 8-bit code was proposed by the committee, since eight bits (octets) would allow two four-bit patterns to productively encode two digits with binary-coded decimal. Nevertheless, all data transmission would be obliged to send eight bits when seven could be pretty enough. The committee decided to use a 7-bit code in order to minimize costs related to data transmission. Taking into consideration that the perforated tape of that time could record eight bits in one position, it also allowed for a parity bit for error checking, if it was needed. Eight-bit machines (with octets as the native data type) that did not use parity checking typically set the eighth bit to 0. The high bit was used some printers in order to enable Italics printing.