Hello,
I need to make routines that can program the COM port and write or read data from it. Like the normal Hyperterminal facility of windows. Please help.

Well, there are three ways to do this:

1) through DOS - just use standart DOS file i/o calls with "files" named COM1, COM2, COM3, COM4
2) through BIOS - http://www.ctyme.com/intr/int-14.htm
3) using direct port i/o

http://www.nondot.org/sabre/os/files/Communication/ser_port.txt is good reference to serial port programming.