[BioC] Query regarding Bioconductor package

[varpal singh]

Respected Mam/Sir,

Myself Varpal singh from india, am doing a project on microarray data
analysis by bioconductor package but am not able to interpretate results. I
want to analysis Affymetrix data by bioconductor. I got result by running
the following commands:

I have a wild and a mutant types each have two replicate i.e Two for wild
and two for mutant.

I got only 137 genes. after the cut-off 0.001 for p value.

The result that you can see in the folowing attached excel files, in which
you can see the fold change value that i dont understand,
Can we predict up/down regulated genes on the basis of Fold change value ??
How is it calculate fold change between four CEL files ???
Is it use average of wild type replicates and mutant type replicates ??

Plz suggest me!!
Thanks and Regards
varpall