[Mspgcc-users] .comm ?

[Garst R. Reese]

.data
        .comm   rxdata,1,1              ;char var
        .comm   rxshift,1,1             ;char var
        .comm   rxbit,2,2               ;short var, aligned

I can't find a reference to meaning .comm in the assembler directives in
as_4.pdf.
Which FM should I be R'ing?
Thanks,
  Garst