In reply to Niyati:
module temp;
initial begin
`ifdef FULL_RATE
$display("I am in full rate");
`endif
`ifdef HALF_RATE
`define HALForQUAD_RATE
`elsif QUAD_RATE
`define HALForQUAD_RATE
`endif
`ifdef HALForQUAD_RATE
$display("I am in else part");
`endif
end
endmodule