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DOS ASCII vs WINDOWS ASCII

Posted on 2004-09-07
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Is there a difference between the DOS and WINDOWS ASCII code page.

If yes which characters are different?

What is the difference between ANSI and ASCII sets???
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Question by:Idarac
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by:Validor
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DOS ASCII is the same as Windows ASCII.  Windows can use many encodings, most are multi-byte character sets and are often called UNICODE character sets.  ASCII is about the only one that is not a multi-byte character encoding and it is the same as the DOS encoding.  Mind you, if you view a DOS file with this encoding, the FONT will probably not reflect the same characters that you would see in DOS.  It is still the same data, though.

ASCII typically refers to the lower 7-bits, or 128 characters of the DOS character set.  ANSI usually refers to the whole 256-character set.  The lower 128 characters or the ANSI set are the ASCII character set.
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by:brettmjohnson
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The 8-bit character sets have 255 possible unique values to represent characters.
The code pages provide a mapping between each of the 255 unique values and
a glyph representing a character.  Unfortunately 255 values is insufficient to encode
all of the character gyphs in Roman character-based languages, let alone glyphs of
non-Roman languages of Africa , the Middle-east, and Asia.   IBM created localized
character mappings that provided mappings for most glyphs used in the local languages.
http://www.microsoft.com/globaldev/reference/oslocversion.mspx

The US ANSI X3.4-1986 specifies the character mapping for characters 0-127
http://www.columbia.edu/kermit/csettables.html

The other code pages usually differ from ANSI set by specifying additional mappings
for character codes 128-255.

[US] MS-DOS ASCII is code page 437, and later code page 850.
[US] Microsoft ASCII is code page 1252

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by:RanjeetRain
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>> Is there a difference between the DOS and WINDOWS ASCII code page.
Code page and the character set are two different things. The code page for the two are different, but character sets are the same.

>> If yes which characters are different?
None.

>> What is the difference between ANSI and ASCII sets???
ANSI is a superset of ASCII and vice versa.

ASCII is a 7 bit character set. Means it has a total of 128 characters. First 27 charatcers are referred to as control characters, as they are used to control many operations in some prominent leagcy OSs, DOS and UNIX for instance. For exampls, under MS-DOS, ASCII character 26 (a <Ctrl + Z> key sequence), is treated as a E-O-F character. ASCII character 7 (a <Ctrl + G> key sequence), sends a beep to the system speaker, character 27 is the <Escape> key.

Many of characters were used in OSs like UNIX in a certain way. While Windows retains the behaviour of the ASCII character set as it is, it does work more comfortably with ANSI, and UNICODE in later versions.

Mind you, an OS CANNOT change a character set, it can only use it differently. Also, what code page a particular character set belongs to, has no significance other than how the OS itself will loacte it.

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by:Validor
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Update to my previous comment...

I was responding under the impression that you were referring to the character set under the DOS operating system, not the DOS ASCII codepage in Windows.  Some of the other responses may be more correct in this respect.
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by:Idarac
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Maybe I should ask what exactly is a code page as opposed to the character set and how do each work?
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RanjeetRain earned 250 total points
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I will *try* to explain.

Character set - A character set is a set of symbols a software uses to interact with a human user. More technically, a character set defines what a representation of a particular string of bits will be, on the I/O devices. A character set is a defined collection of symbols.

Code page - A code page is a location (in the main memory owned by the OS) where the definition of a character set is located. An OS may have more than one code pages, each one to support the characters people around the globe are more used to. For instance, an English user doesn't use accented vowels. A French or Spanish user may. Hence, the need of different code pages.

A code page is, probably, called so because, it is a memory page that holds the definition of a character set and its representation.
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