Using following program bold characters can be displayed. Note that this program takes help of UNIX facilities. This may not work on PC based simulators.
module bold;
initial begin
$display ("Normal Text");
$display ("\033[1mBold Text");
$display ("\033[mSwitch back to Normal Text.....");
$display ("\033[7mInverse Text.");
$display ("\033[mSwitch back to Normal Text.....");
$display ("\033[1mBold Text \033[mfollowed by \033[7mInverse text \033[m");