@LTK:
Much computer storage is in binary, though, especially with huge datasets; if the code were stored in ASCII, then it would compress dramatically using common algorithms, but I know from an article on the subject I've just read that gzip compresses a conventionally stored genome by only about 35%.
@May:
The genome is the actual sequence of bases (A, T, C, G) in all the DNA of the individual; i.e. the definition of all the genes on all the chromosomes (I don't know if mitochondrial DNA is included). Essentially it is the complete chemical formula of the whole lot. The term "sequencing" DNA is used, because the process is determining that sequence.