ASCII format CEL ASCII format http://www.affymetrix.com/support/developer/powertools/changelog/gcos-agcc/cel.html, accessed 22 May 2013. Allyson Lister CEL ASCII format is ASCII data format specification created by Affymetrix similar to the Windows INI format. The CEL format stores the results of the intensity calculations on the pixel values of the DAT file. This includes an intensity value, standard deviation of the intensity, the number of pixels used to calculate the intensity value, a flag to indicate an outlier as calculated by the algorithm and a user defined flag indicating the feature should be excluded from future analysis. The file stores the previously stated data for each feature on the probe array.