AIX endian again Post: 17923

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Top Forums UNIX for Advanced & Expert Users AIX endian again Post 17923 by Perderabo on Thursday 21st of March 2002 08:16:30 AM

03-21-2002

Administrator Emeritus

Endian-ness in a cpu arises because we need to specify multi-byte integers with a byte address.

In the '60's I worked on an IBM 1130. It was a 16 bit machine and had no byte addressing. Address 0 was a 16 bit word. Address 1 was the next 16 bit word. There is no way to determine an endian-ness on a system like this.

I have never heard of any cpu that even allows bit addressing. If there was one, and if it required the programmer to specify a bit address for a byte, then we would need to worry about the endian-ness of a single byte.

The only time that byte endian-ness becomes apparent is when a byte is transmitted across a serial data line. TCP/IP is an example of this, and in TCP/IP, bytes are big-endian. (or more accurately, octets are big-endian, since TCP/IP does not assume that bytes are 8 bits). Contrary to your comment, this is what I regard as "normal". Most other serial protocols are also big-endian, at least most of the modern ones are.

On the other hand, RS-232 is little-endian. So is the old current-loop interface. The earlier teletype protocols are before my time, but I think that they were little-endian (but I'm not sure). These protocols never need to transit a multi-byte integer and they need to support both 7 bit and 8 bit characters.

So unless you are designing an i/o card to transmit bytes in a bit serial fashion, you can safely ignore this issue with every cpu that I have heard of.

But it's hard to be sure that something doesn't exist, so if someone out there knows about a cpu that requires a bit address for addressing its bytes, I would be very interested in the details of it.

Perderabo

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LEARN ABOUT DEBIAN

tslmendian

TSLMENDIAN(1)						User Contributed Perl Documentation					     TSLMENDIAN(1)

NAME

       tslmendian - change the byte-order of sunpinyin's threaded back-off language model

SYNOPSIS

       tslmendian [option]

DESCRIPTION

       slmendian converts the binary language model files used by SunPinyin from big-endian to small-endian or vice versa.

OPTIONS

       -e endian
	   Specify the output-lm-file's endian-ness. It can be le or ge. If not given, tslmendian uses the host's endian-ness.

       -v  Prints out the endian-ness of input-lm-file.

       -i input-lm-file
	   Identify the input file of convert. Generally, this file is generated by slmthread or tslmpack.

       -o out-lm-file
	   Identify the output file of convert.

NOTES

       The converted output file is equivalent to the input. But if you compare the output of tslminfo of both files, the ARPA file generated by
       tslminfo may different. This is due to the different precision in different machines.

       And due to uninitialized padding data in data structure, the checksum of the original data file may different from the converted-back file,
       even though they are identical from SunPinyin's point of view.

AUTHOR

       Originally written by Kov. Chai <tchaikov.gmail.com>.  Currently maintained by Kov.Chai <tchaikov@gmail.com>.

SEE ALSO

       slmthread(1). tslminfo, tslmpack.

perl v5.14.2							    2012-06-09							     TSLMENDIAN(1)