From: http://www.techadvice.com/tech/C/ComPort_TS.htm
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It can be switched off in BIOS of your PC. In Apple Macintosh there's no COM1 at all.
COM1 and COM2 originally referred to the serial port interfaces on a PC. Now they can refer to any port, virtual or physical.
com1,com2 com3
IRQs 3 is reserved for the COM1 port.
The "com" ports are computer, serical communications ports (normally RS-232).
COM1 and COM3, IRQ4
well COM1, COM2, COM3, and COM4 are sometimes configured as Serial Ports.
Already the windows xp have serial port.so no need to go for serial port driver.
COM1-IRQ 4, memory addresses 03F8-03FF COM2-IRQ 3, memory addresses 02F8-02FF COM3-IRQ 4, memory addresses 03E8-03EF COM4-IRQ 3, memory addresses 02E8-02EF pg. 396
COM1 is seldom used for anything these days, and may not even be mapped to a physical device on newer systems. Its primary purpose is/was to serve as a communications port, either to an internal or external modem, or as a connection into a mainframe computer. It has also seen some use as a general purpose expansion port and been used to attach mice, printers, and cameras to a computer.
The serial ports are named ttyS0, ttyS1, etc.And usually correspond respectively to COM1, COM2, etc. in DOS/Windows
No. Both COM ports and USB ports are serial interfaces, but the COM interfaces are driven by single device UARTs.