What is ASCII?
Date: 12/19/2000 at 22:59:50 From: Monique Subject: ASCII I am converting binary numbers to ASCII and I don't really know what ASCII is. Can you tell me, please? Thank you.
Date: 12/20/2000 at 13:33:59 From: Doctor TWE Subject: Re: ASCII Hi Monique - thanks for writing to Dr. Math. ASCII is an acronym (an abbreviation that's pronounced like a word) that stands for the American Standard Code for Information Interchange. It is not a way of representing numbers, but rather a way of representing alpha-numeric information (text) in binary. Most computers today use ASCII, or some extension of it, for storing and transmitting text-based data. Standard ASCII uses 7 bits to represent each character. But since only 2^7 = 128 different characters can be represented this way, some computers have developed "extended ASCII" codes that use 8 (or more) bits per character, thus allowing more characters in the character set. The "IBM PC Extended Character Set" used in PCs is an example of an extended ASCII code. As an example of ASCII, here is how "Dr. TWE" would be represented in ASCII: char. ASCII (binary) Hex Dec ----- -------------- --- --- D 100 0100 44 68 r 111 0010 72 114 . 010 1110 2E 46 space 010 0000 20 32 T 101 0100 54 84 W 101 0111 57 87 E 100 0101 45 37 In the chart above, I have represented the ASCII codes in binary, as the computer would represent them. Since writing ASCII codes in binary requires a lot of space (and is prone to errors), we often use hexadecimal or decimal as a "shorthand" notation. I have included the hex and decimal equivalents on the chart above. For a complete chart of standard ASCII, see "Standard ASCII Chart" at: http://distance_ed.avc.edu/avcoll/faculty/ebeyer/CA103/StandardASCII_Chart.htm Since most computers use 8 bits to represent a character, this chart adds a space (a 0) at the beginning of each character to "fill out" the 8 bits. For a chart of the IBM PC Extended Character Set, see "The IBM (DOS) Extended ASCII Character Set" at: http://www.sageservices.bc.ca/ascii-codes.html For information on converting among binary, hexadecimal and decimal see our "Number Bases" FAQ page at: http://mathforum.org/dr.math/faq/faq.bases.html I hope this helps. If you have any more questions, write back. - Doctor TWE, The Math Forum http://mathforum.org/dr.math/
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