XGEN: How EBCDIC to ASCII Translation Takes Place

ID: Q194872

The information in this article applies to:

Microsoft Exchange Server, versions 5.0, 5.5

SUMMARY

The connector gateways that communicate with mainframe systems (such as PROFS) must be able to translate ASCII characters to EBCDIC and back to ASCII. This article documents how this process occurs.

MORE INFORMATION

If the host attempts to send the letter D (which is C4 in EBCDIC), it has to find the ASCII equivalent of the letter D in special files representing the codepages in use on either system. The connector opens the proper host to Exchange Server file, accesses the offset of 000000C4, looks up the value in the column (the value is 44), and translates the character to 44, which is the ASCII representation of the letter D.

There are eight such files located in the Exchsrvr\Connect\Exchconn directory that contain the character mappings. These files are:

1252_256.csm Exchange -> host
1252_500.csm Exchange -> host
850_256.csm Exchange -> host
850_500.csm Exchange -> host
256_1252.csm host -> Exchange
500_1252.csm host -> Exchange
256_850.csm host -> Exchange
500_850.csm host -> Exchange

Note that the files are in pairs for each direction. The file names represent the codepages in use on either system. If a file that is for Exchange --> host is opened in a regular hex editor (that only knows ASCII) the values in the right column will be incorrect. This is because the editor is attempting to read them as ASCII while they are the EBCDIC representations).

If a file is opened in a hex editor (a snippet from 256_1252.csm is given below) the right column shows the character to be translated and the byte columns in the middle show the resulting character with the plain-text representation on the far right.

NOTE: The following example should be one line:


000000C0  7B 41 42 43 44 45 46 47  48 49 AD F4 F6 F2 F3 F5
{ABCDEFGHI......

Keywords :
Version : WinNT:5.0,5.5
Platform : winnt
Issue type : kbhowto