Microsoft COM ports
From the earliest Microsoft operating system based, personal computers, to its latest used today, Microsoft has labelled its serial communications ports as COMn ports, with ‘n’, is an integer.
The first use of COM port tied them directly to a physical RS232 serial communications port. The first RS232 port being COM1 and the second RS232 port being COM2.
With the movement away from RS232 ports to USB ports, together with operating system developments, the COM has moved away from being tied to a physical port and now points to a virtual port identity.
The USB has it’s own physical hardware port identity. To link the physical identity to a virtual COM port identity, Microsoft Windows now has an internal COM Port Database.
This database, amongst other things, provided the software link between a COMn port number and the hardware USB port number.
The Microsoft Windows application, USBTreeView is very useful in understanding your USB topology and the assignment of COM ports in Microsoft Windows to USB ports.
The Microsoft Windows application USB Drive Letter Manager is useful in reallocating the Windows com port assignment to a physical USB port.