PROBLEM LOADING THE covdesc FILE IN SIMPLEAFFY

Dear R users:
Thanks to you all, I am finding very useful previous questions and answers from other users.
But I was not able to find out what I am doing wrong when trying to load the covdesc file.
I have a folder in my directory that contains all 18 CEL files and also the covdesc (extension .prn - is this
the right one?). Since I was able to run the gcrma normalization so the working directory maybe well set,
what I got is the next:

> raw.data <- ReadAffy()
> gcrma.eset <- call.exprs(raw.data, "gcrma")
Loading required package: AnnotationDbi

Adjusting for optical effect..................Done.
Computing affinities.Done.
Adjusting for non-specific binding..................Done.
Normalizing
Calculating Expression
> raw.data <- read.affy() ##read data in working directory
Error in file(file, "rt") : cannot open the connection
In addition: Warning message:
In file(file, "rt") :
  cannot open file './covdesc': No such file or directory
> raw.data<- read.affy("covdesc")
Error in file(file, "rt") : cannot open the connection
In addition: Warning message:
In file(file, "rt") :
  cannot open file './covdesc': No such file or directory

thanks in advance for any help.
Miriam