Ascii text

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Ascii text
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ASCII abbreviated from American Standard Code For Information Interchange, is a standard for character encoding in computer systems. Name of this standard is recognisable and used for long time, however IANA organisation strongly suggest to use US-ASCII name, to emphasise origins of standard and languages supported[1]. Currently it is widely used and recognised as the most popular mechanism used for character encoding. ASCII contains a set of 128 characters which includes letters, digits, symbols and control sequences. ASCII is a United States version of the International Standard for Information Processing. This character encoding system uses 7-bit character sets. Main goal of ASCII is to interchange information among data processing systems, computers and every equipment associated with such machines [2].

Mechanism

ASCII works in similar way as other character encoding systems (e.q. MCS - Multinational Character Set). Standard assumes that each character has a binary code assigned, which is representing the position of character in an arbitrarily ordered set of characters (ASCII table)[3]. For example, letter F has decimal code 70 which in binary equals to 1000110 whereas number 6 has decimal representation and position in table equal to 54 which in binary can be represented as: 110110. Numeric representation of letter is convenient for computer systems as they operate on numbers. ASCII provides good solution for comparing letters and words as they can be compared using mathematical operators like: greater than, less than or equals[3].

ASCII set

ASCII set contains many different symbols and characters. First elements of ASCII table are Control Characters which can be divided in 6 groups[2]:

  • Transmission Control Characters - used for controlling the transmission between devices,
  • Format Effectors - intended to control the layout, formatting and positioning of text especially for displays or printers,
  • Code Extension Control Characters - used for extending the character set of code,
  • Device Control Characters - intended to control devices connected to main system,
  • Information Separators - used to separate and divide data in to logical groups,
  • Other Control Characters - used to control characters and situations that are not suited to any other group.

Control characters have decimal representation in numbers 0 - 32. However, there is also one more character used for deleting other symbols and it is called DEL and is positioned at the end of table with number 127. Values between 32 and 127 are representing other characters that can be used by user to create text. Special characters like question mark, quotes, exclamation point are first in the order and are represented by values from 33 to 64 with exception of values 48 - 57 which stand for numbers 0 - 9. Upper case letters are represented by values 65 - 90. Then ASCII table contains few other special characters like brackets. Lower case letters are represented by range 97 - 122. ASCII table ends with braces, vertical line, tilde and mentioned before DEL special character[4].

ASCII art

As ASCII consists of characters it can be used to assemble words, sentences but also other representations of thought. Using proper algorithms and mechanism it is possible to construct images using letters arranged in certain way. ASCII art can be divided into two groups. Tone-based art which main goal is to achieve the graphic by density of glyph. Other group, structure-based art uses the line of glyph to represent graphics and especially its outlines and borders. Structure based art is using smaller amounts of ASCII characters as it is not filling the insides of objects. ASCII art can be created manually and using software programs that generate graphics automatically[5].

Footnotes

  1. Character Sets, (ang.), iana.org.
  2. 2.0 2.1 ANSI, X. (1986). 4: Coded Character Set—7-Bit American National Standard Code for Information Interchange, Am. Nat’l Standards Inst., New York. ISO 690
  3. 3.0 3.1 Fisher, E. G., & Gilbert, P. D. (1993), U.S. Patent No. 5,225,833, Washington, DC: U.S. Patent and Trademark Office
  4. Weiman D., (2012), Decimal - Binary - Octal - Hex – ASCII Conversion Chart
  5. Miyake, K., Johan, H., & Nishita, T. (2011), An interactive system for structure-based ASCII art creation., Proc. NICOGRAPH Int., 4-3.

References

Author: Michał Bałos