What is ANSI encoding format? Is it a system default format? In what way does it differ from ASCII?
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When using single-byte characters, the ASCII format defines the first 127 characters. The extended characters from 128-255 are defined by various ANSI code pages to allow limited support for other languages. In order to make sense of an ANSI encoded string, you need to know which code page it uses.
Strictly speaking, there is no such thing as ANSI encoding. Colloquially the term ANSI is used for several different encodings:
I remember when "ANSI" text referred to the pseudo VT-100 escape codes usable in DOS through the ANSI.SYS driver to alter the flow of streaming text.... Probably not what you are referring to but if it is see http://en.wikipedia.org/wiki/ANSI_escape_code
Just in case your PC is not a "Western" PC and you don't know which code page is used, you can have a look at this page: National Language Support (NLS) API Reference
[Microsoft removed this reference, take it form web-archive National Language Support (NLS) API Reference
Or you can query your registry:
C:\>reg query HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Nls\CodePage /f ACP
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Nls\CodePage
ACP REG_SZ 1252
End of search: 1 match(es) found.
C:\>
ANSI (aka Windows-1252/WinLatin1) is a character encoding of the Latin alphabet, fairly similar to ISO-8859-1. You may want to take a look of it at Wikipedia.
Basically "ANSI" refers to the legacy codepage on Windows. See also an article by Raymond Chen on this topic:
The source of this comes from the fact that the Windows code page 1252 was originally based on an ANSI draft, which became ISO Standard 8859-1.
The first 127 characters are identical to ASCII in most code pages, the upper characters vary, though.
However, ANSI does not automatically mean CP1252 or Latin 1.
All confusion notwithstanding you should simply avoid such issues nowadays and use Unicode.
Once upon a time Microsoft, like everyone else, used 7-bit character sets, and they invented their own when it suited them, though they kept ASCII as a core subset. Then they realised the world had moved on to 8-bit encodings and that there were international standards around, such as the ISO-8859 family. In those days, if you wanted to get hold of an international standard and you lived in the US, you bought it from the American National Standards Institute, ANSI, who republished international standards with their own branding and numbers (that's because the US government wants conformance to American standards, not international standards). So Microsoft's copy of ISO-8859 said "ANSI" on the cover. And because Microsoft weren't very used to standards in those days, they didn't realise that ANSI published lots of other standards as well. So they referred to the standards in the ISO-8859 family (and the variants that they invented, because they didn't really understand standards in those days) by the name on the cover, "ANSI", and it found its way into Microsoft user documentation and hence into the user community. That was about 30 years ago, but you still sometimes hear the name today.
Technically, ANSI should be the same as US-ASCII. It refers to the ANSI X3.4 standard, which is simply the ANSI organisation's ratified version of ASCII. Use of the top-bit-set characters is not defined in ASCII/ANSI as it is a 7-bit character set.
However years of misuse of the term by the DOS and subsequently Windows community has left its practical meaning as “the system codepage of whatever machine is being used”. The system codepage is also sometimes known as ‘mbcs’, since on East Asian systems that can be a multiple-byte-per-character encoding. Some code pages can even use top-bit-clear bytes as trailing bytes in a multibyte sequence, so it's not even strict compatible with plain ASCII... but even then, it's still called “ANSI”.
On US and Western European default settings, “ANSI” maps to Windows code page 1252. This is not the same as ISO-8859-1 (although it is quite similar). On other machines it could be anything else at all. This makes “ANSI” utterly useless as an external encoding identifier.
ASCII just defines a 7 bit code page with 128 symbols. ANSI extends this to 8 bit and there are several different code pages for the symbols 128 to 255.
The naming ANSI is not correct because it is actually the ISO/IEC 8859 norm that defines this code pages. See ISO/IEC 8859 for reference. There are 16 code pages ISO/IEC 8859-1 to ISO/IEC 8859-16.
Windows-1252 is again based on ISO/IEC 8859-1 with some modification mainly in the range of the C1 control set in the range 128 to 159. Wikipedia states that Windows-1252 is also refered as ISO-8859-1 with a second hyphen between ISO and 8859. (Unbelievable! Who does something like that?!?)
Source: Stackoverflow.com