# Which format is the most raw format

I wanted information regarding which format is considered the most raw from an illumina sequencer ?

1. fasta
2. fastq
3. bcl
4. bam
As per my research it should be bcl but I am not sure.
• What do you mean by “raw”? None of the files you’ve listed are “raw” in any real sense. In fact, FASTQ and BCL are more or less equivalent, just stored in different ways. For the difference between FASTA, FASTQ and BAM, refer to bioinformatics.stackexchange.com/a/385/29. Jun 1 '21 at 13:56

For any useful application you would convert them to fastq (e.g. using illumina bcl2fastq).