Question How does a PC know what a connected device is?

[pccobbler]

When I connect a CD-ROM drive to a PC, Device Manager (for Windows) knows what type of hardware it is. How is that done? Is there a textfield with "CD-ROM" in it in the device? Or is it a numeric field, for example, "12345" which translates to CD-ROM? If someone wants to point me to a technical webpage that explains this, wonderful.

 

[rgd1101]

device id

 

[fzabkar]

The CD is an ATAPI device. It returns ID info in response to an IDENTIFY PACKET DEVICE command.

https://people.freebsd.org/~imp/asiabsdcon2015/works/d2161r5-ATAATAPI_Command_Set_-_3.pdf (page 163)

 

[punkncat]

One of the aspects I have really appreciated since W7 was for the update system to know what drivers to get. Before that you had to manually look up the Hardware ID and find suitable drivers (if you lost your drivers disk).

 

[CountMike]

Simple, "Plug &play" devices have some kind of firmware aka, Bios that supply all relevant data to OS so it "knows" what device is as well as it's capabilities and can enact all appropriate settings for it as well as retrieve drivers needed. Before that invention, all had to be set manually taking into account that DMA. interrupts and others do not clash with existing ones and are in specified range or needed a driver and .inf file to tell the OS about it
First attempts were not fully useful so it was often referred to as "Plug&PRAY".