In that case you just need to usea terminal program from windows such as hyperterminal which will allow you to send any charcter string overyour rs232 port so there is no need to write that code.Atyour clock you just need to define what commands you want to use to set the hour and minutes,so you could send say character'h' followed by a signed byte to set the hours,'m' followed by a signed byte to set the minutes,and some command to startor stop the clcock..