256 vs. 1024 channels Hmmmmmm

JTrotter@PharMingen.com JTrotter at PharMingen.com
Thu Mar 21 14:49:35 EST 2002


     Different devices may allocate different block sizes in their file
allocation procedures for the same files. Also, forgive me for stating what
may be obvious - but 256 channel data (8 bits) requires 1 byte (8 bits)
per data point, 1024 channel data (10 bits) requires 2 bytes (16 bits)
because most systems use bytes as the "smallest" unit. Similarly, the newer
digital systems require 4 bytes (32 bits) for 18 bit, 20 bit, 24 bit, and
32 bit data. So, expect the binary part of a FCS file double from 256 to
1024 channel data, and for it double again if 32 bits are required. Since
FCS files have a short header and variable TEXT info section, the initial
TEXT part of the FCS file will typically vary in size from manufacturer to
manufacturer, but remain about the same modest size no matter what the
binary portion requires.

     Best regards,


Joseph Webster <J.Webster at centenary.usyd.edu.AU> on 03/19/2002 08:37:07 PM

To: cyto-inbox
Subject:  Re: 256 vs. 1024 channels Hmmmmmm

Many thanks to all those who showed me the bullet hole in my shoe...

A few days ago I wrote:
> > .... but remember that a 1024-channel data file is four times
> > bigger than the same data in 256 channels.

After a prompt from Mario, I checked this morning and that statement
is wrong!
I remember a factor of four in the (good old?) days of HP computer
and LYSYS II, but had never bothered to check that change in newer

Testing this morning, my 256-channel file was 72078 bytes while the
same data (test pulses) in 1024-channel was 142078 bytes, or about
double the file size.
Just to confuse matters though, the Mac file system uses 130Kb and
195Kb respectively for the same two files on a 2Gb disk....

Now the accuracy of my memory is quite a different matter... ;~)
Anyone still running a FACScan with LYSIS?


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