GN_Flw, Write character to filter

Register parameters

RST 20H, DEFW $2609

IN:
     IX = filter handle
     A = character to write to filter

OUT, if call successful:
     Fc = 0
     A = A(in)
OUT, if call failed:
     Fc = 1
     A = error code:
          RC_HAND ($08), bad filter handle
          RC_FLF ($0A), filter is full

Registers changed after return:
     A.BCDEHL/IXIY same
     .F....../.... different

Related calls

GN_Flc, close filter
GN_Flf, flush filter
GN_Flo, open filter
GN_Flr, read from filter
GN_Fpb, push back into filter