First, the need for coding of
E-mail can only send text messages in ASCII (American National Standard Code for Information Interchange) format, ASCII code is 7-bit code, non-ASCII file format in the transmission process will need to be compiled 7 bit ASCII code, and then it can be transmitted via E-mail; if not encoded, because the 7-bit ASCII code and restrictions are broken down in the course of transmission, will only make the addressee after seeing a jumble of decomposition ASCII characters. After encoded files can be transferred smoothly during the transfer process, it is not in danger "amputated one" of. But the addressee must have the appropriate decoding program, this will be encoded to restore things to see what the sender information to be transmitted Yes.
One thing to note: Most people think that "text files do not require coding," but our Chinese belong to eight character code, not a standard ASCII code format, because the Chinese are prevailing in the country of text, so most mail servers are capable of processing documents GB inner code, it is not necessary to make such encoding / decoding operations, it may be directly transmitted. But if you want to send a message to the Chinese abroad, we need to go through this conversion to transfer, because foreign mail server is unrecognizable in the Chinese yards. Chinese code when after some code is not supported within the Chinese relay host, still be cut off one, resulting in fragmented files can not be read caries and encoded Chinese e-mail, the recipient will receive the decoded file restore, also need to have Chinese Chinese information system to see written.
Two, three common encoding standards
● UU encoding (the Unix-to-Unixencoding)
the uuencode and uudecode originally unix encoding and decoding system used by the program, and later rewritten in DOS program can be executed. When non-ASCII file transfer at an early stage, this is the most common UU encoding.
The method used was: Before mail, to the original file in DOS program uuencode.exe encoding into ASCII file, and then sent the message. That the recipient received the message, with uudecode.exe program to restore files.
Windows-based programs have similar wincode winzip and so on.
using the principles wincode and uuencode and uudecode under DOS is no different, just easier in the Windows interface operation. In addition to supporting outer coding wincode UU supports MIME, Binhex encoding format, rather wide range of applications.
UU encoding described above not only be assigned Chinese characters. You want to send any document comprises exe can send binary files, such addressee receiver → → reduction decoding step of transmitting a coding →.
● MIME standard (Multipurpose Internet Mail Extentions)
UU encoding to solve the problem of E-mail can only send ASCII file. But in this way it is actually not very convenient, so they developed a new coding standard, its full name is the Multipurpose Internet Mail Extentions, usually translated as "multimedia messaging mode." As the name suggests, it can send multimedia files, sending e-mail with attached files in various formats.
MIME standard Internet e-mail has now become mainstream. Its advantage is based on the object as packaging, can be packaged with a variety of different file transfer. As long as the sender file selected to be transmitted, it is encoded in real-time transmission, the recipient also receive real-time decoding software restore fully automated, very convenient. Of course, a prerequisite is that both sides must have this software function, or else the sender easily sent out the letter, but the recipient of the software without this feature, you can not restore it, you can see that is a big the garbage heap. This way, users do not need to know how it is encoded / decoded. Even if only with words written in the letter, as it is packed and sent. If you want to send multimedia files, as long as the selected file to do the action, sent after the election, the rest of the work is done automatically by e-mail software.
Because of the convenience of MIME, more and more e-mail software in this way. (Eudora e-mail software, we are now the most commonly used, NetscapeMail, InternetMail is to use MIME and other ways, so that we can so easily send and receive e-mail.) MIME is defined by a specification can be said to be a collectively.
Encoding fact able to meet this specification is not a single one, can be transferred smoothly as long as consistent with this MIME specifications. To freight as an analogy, if sent freight shipping company policy specification is the size of one cubic meter box can be checked, it does not limit must use wooden or tin trunk, as long as one cubic meter size, the shipping company to help you served. As for the box you are loading food or books or clothes or dress is also not limited mixing, that is to say, a variety of file formats can be sent together.
On the above example, the "big one cubic meter cargo ramp is standard, which is our MIME specifications. Wooden or tin trunk is encoding, and now we take a look at what you have" kind of box "can be selected define .MIME two encoding types: Base64 rules and QP (Quote-Printable) .QP is a 7-bit coded data without repetition in only the 8-bit data into 7 .QP encoding applies to the non-ASCII text content, for example, our Chinese documents, while Base64 encoding rules, the entire file is re-encoded into seven, normally used to transfer binary files. different coding will affect the way Colonel after the file has MIME encoding function E-mail software most you can automatically determine what the message is encoded using, and then automatically selects a QP or Base64 decoding.
QP coding method, is a two-byte hexadecimal value represents, and then added to the front "=." so we see through the text after QP coding usually look like this: = A4j = AEa = A6n = A1I = A7 = DA = AC0 = B1 = E7 = A9s = A7g = A1A = AB = DC = B0 = AA = B
After the Base64 encoded text is usually: pGquYaZuoUmn2qxPseepc6dnoUGr3LCqv70ms773t3ymYqa5plakaq5hptu if you use e-mail software supports the MIME standard, then the process receive correspondence is not see such a mess of characters. But if, unfortunately, no such recipient MIME support software, which is above what he saw that a large section of the symbol. But do not worry, you can still first this "bible" archive, and then use some decode software to translate it back.
● Binhex coding
Binhex encoding methods commonly used in the Mac machine, on a PC is a coding way less used. General e-mail software on the PC, also majority support MIME specifications, there is little support Binhex format. In the popular e-mail software, only Eudora has such a function, it can be directly interpreted coding Binhex, if you have received this e-mail encoded by the Binhex, and your mail software does not support Binhex Eudora or other software formats . It is also starting a program to decode Binhex interpretation. There is a shareware Binhex3.exe have this feature, which can be found in many FTP sites.
In Windows, you can also be decoded by wincode we described earlier. This article describes UU-encoded, MIME and Binhex can be treated with it. But unfortunately, for MIME, Base64 encoding only deal with the. If you could add the function of QP, really traveled the world relied on the.
Almost become standard in MIME now, with software to do a MIME support sending and receiving E-mail, which are encoding / decoding work will be done automatically, will not bring trouble to you.
E-mail can only send text messages in ASCII (American National Standard Code for Information Interchange) format, ASCII code is 7-bit code, non-ASCII file format in the transmission process will need to be compiled 7 bit ASCII code, and then it can be transmitted via E-mail; if not encoded, because the 7-bit ASCII code and restrictions are broken down in the course of transmission, will only make the addressee after seeing a jumble of decomposition ASCII characters. After encoded files can be transferred smoothly during the transfer process, it is not in danger "amputated one" of. But the addressee must have the appropriate decoding program, this will be encoded to restore things to see what the sender information to be transmitted Yes.
One thing to note: Most people think that "text files do not require coding," but our Chinese belong to eight character code, not a standard ASCII code format, because the Chinese are prevailing in the country of text, so most mail servers are capable of processing documents GB inner code, it is not necessary to make such encoding / decoding operations, it may be directly transmitted. But if you want to send a message to the Chinese abroad, we need to go through this conversion to transfer, because foreign mail server is unrecognizable in the Chinese yards. Chinese code when after some code is not supported within the Chinese relay host, still be cut off one, resulting in fragmented files can not be read caries and encoded Chinese e-mail, the recipient will receive the decoded file restore, also need to have Chinese Chinese information system to see written.
Two, three common encoding standards
● UU encoding (the Unix-to-Unixencoding)
the uuencode and uudecode originally unix encoding and decoding system used by the program, and later rewritten in DOS program can be executed. When non-ASCII file transfer at an early stage, this is the most common UU encoding.
The method used was: Before mail, to the original file in DOS program uuencode.exe encoding into ASCII file, and then sent the message. That the recipient received the message, with uudecode.exe program to restore files.
Windows-based programs have similar wincode winzip and so on.
using the principles wincode and uuencode and uudecode under DOS is no different, just easier in the Windows interface operation. In addition to supporting outer coding wincode UU supports MIME, Binhex encoding format, rather wide range of applications.
UU encoding described above not only be assigned Chinese characters. You want to send any document comprises exe can send binary files, such addressee receiver → → reduction decoding step of transmitting a coding →.
● MIME standard (Multipurpose Internet Mail Extentions)
UU encoding to solve the problem of E-mail can only send ASCII file. But in this way it is actually not very convenient, so they developed a new coding standard, its full name is the Multipurpose Internet Mail Extentions, usually translated as "multimedia messaging mode." As the name suggests, it can send multimedia files, sending e-mail with attached files in various formats.
MIME standard Internet e-mail has now become mainstream. Its advantage is based on the object as packaging, can be packaged with a variety of different file transfer. As long as the sender file selected to be transmitted, it is encoded in real-time transmission, the recipient also receive real-time decoding software restore fully automated, very convenient. Of course, a prerequisite is that both sides must have this software function, or else the sender easily sent out the letter, but the recipient of the software without this feature, you can not restore it, you can see that is a big the garbage heap. This way, users do not need to know how it is encoded / decoded. Even if only with words written in the letter, as it is packed and sent. If you want to send multimedia files, as long as the selected file to do the action, sent after the election, the rest of the work is done automatically by e-mail software.
Because of the convenience of MIME, more and more e-mail software in this way. (Eudora e-mail software, we are now the most commonly used, NetscapeMail, InternetMail is to use MIME and other ways, so that we can so easily send and receive e-mail.) MIME is defined by a specification can be said to be a collectively.
Encoding fact able to meet this specification is not a single one, can be transferred smoothly as long as consistent with this MIME specifications. To freight as an analogy, if sent freight shipping company policy specification is the size of one cubic meter box can be checked, it does not limit must use wooden or tin trunk, as long as one cubic meter size, the shipping company to help you served. As for the box you are loading food or books or clothes or dress is also not limited mixing, that is to say, a variety of file formats can be sent together.
On the above example, the "big one cubic meter cargo ramp is standard, which is our MIME specifications. Wooden or tin trunk is encoding, and now we take a look at what you have" kind of box "can be selected define .MIME two encoding types: Base64 rules and QP (Quote-Printable) .QP is a 7-bit coded data without repetition in only the 8-bit data into 7 .QP encoding applies to the non-ASCII text content, for example, our Chinese documents, while Base64 encoding rules, the entire file is re-encoded into seven, normally used to transfer binary files. different coding will affect the way Colonel after the file has MIME encoding function E-mail software most you can automatically determine what the message is encoded using, and then automatically selects a QP or Base64 decoding.
QP coding method, is a two-byte hexadecimal value represents, and then added to the front "=." so we see through the text after QP coding usually look like this: = A4j = AEa = A6n = A1I = A7 = DA = AC0 = B1 = E7 = A9s = A7g = A1A = AB = DC = B0 = AA = B
After the Base64 encoded text is usually: pGquYaZuoUmn2qxPseepc6dnoUGr3LCqv70ms773t3ymYqa5plakaq5hptu if you use e-mail software supports the MIME standard, then the process receive correspondence is not see such a mess of characters. But if, unfortunately, no such recipient MIME support software, which is above what he saw that a large section of the symbol. But do not worry, you can still first this "bible" archive, and then use some decode software to translate it back.
● Binhex coding
Binhex encoding methods commonly used in the Mac machine, on a PC is a coding way less used. General e-mail software on the PC, also majority support MIME specifications, there is little support Binhex format. In the popular e-mail software, only Eudora has such a function, it can be directly interpreted coding Binhex, if you have received this e-mail encoded by the Binhex, and your mail software does not support Binhex Eudora or other software formats . It is also starting a program to decode Binhex interpretation. There is a shareware Binhex3.exe have this feature, which can be found in many FTP sites.
In Windows, you can also be decoded by wincode we described earlier. This article describes UU-encoded, MIME and Binhex can be treated with it. But unfortunately, for MIME, Base64 encoding only deal with the. If you could add the function of QP, really traveled the world relied on the.
Almost become standard in MIME now, with software to do a MIME support sending and receiving E-mail, which are encoding / decoding work will be done automatically, will not bring trouble to you.
Reproduced in: https: //www.cnblogs.com/tjdxlmy/archive/2009/10/23/1588496.html