Page Comparison

In:
        A = EP_REQ
        C = slot number (0, 1, 2 or 3)

Out:
   Success, File Area (or potential) available:
        Fc = 0,
             BHL = pointer to File Header for slot C (B = absolute bank of slot).
                   (or pointer to free space in potential new File Area).
               C = size of File Eprom Area in 16K banks
             Fz = 1, File Header found
                  A = "oz" File Eprom sub type
                  D = size of card in 16K banks (0 - 64)
             Fz = 0, File Header not found
                  A undefined
                  D undefined
   Failure:
        Fc = 1,
             C = C(in)
             A = RC_ONF (File Eprom Card/Area not available; possibly no card in slot)
             A = RC_ROOM (No room for File Area; all banks used for applications)

Registers changed after return:
   .....E../IXIY same
   AFBCD.HL/.... different