Alternative Refence Allele in PLINK2 data files

Question

[carlstat123]

Hello,

In PLINK2 file formats, can we represent alternative allele as 0 and reference allele as 1. Or do we need to specify them using A C T or G?

As an example:

In .pvar file we have two columns name ALT and REF. Can these be denoted by using 0 and 1 ?

Thanks.