ASCII format CDF ASCII format http://www.affymetrix.com/support/developer/powertools/changelog/gcos-agcc/cdf.html, accessed 22 May 2013 Allyson Lister The CDF ASCII format is an ASCII data format specification created by Affymetrix similar to the Windows INI format. This format describes the layout for an Affymetrix GeneChip array. An array may contain Expression, Genotyping, CustomSeq, Copy Number and/or Tag probe sets. All probe set names within an array are unique. Multiple copies of a probe set may exist on a single array as long as each copy has a unique name.