The value returned in the COMPATIBLE ID (CID) key by a printer may have any value listed in an INF file, as described in the section Generating Unique Plug and Play Device IDs. Plug and Play IDs assigned to legacy parallel port devices which have driver support in Windows 95 may also be returned.
The CID values returned by a printer should be carefully chosen by printer vendors. If your device returns a CID which is an exact match for a device ID for another vendor's device, ensure you have license rights from the device driver manufacturer to install the compatible device driver. Microsoft will provide CID values for many of the printer drivers shipped with Windows 95 and vendors are encouraged to freely use those values in the CID keys returned by their printers.
The syntax of the string returned from a printer as a CID value is important and will differ slightly depending upon what the printer is reporting itself being compatible with:
For example, suppose the INF file contains the following entry:
"Sample Printer"=X.DRV,LPTENUM\Sample_Printer_CompaAAA2
This INF file entry describes a printer that displays the printer name Sample Printer, is supported by the driver X.DRV. The procedure described in the section Generating Unique Plug and Play Device IDs generates the device ID Sample_Printer_CompaAAA2. The Plug and Play device ID has the enumerator prepended to it, resulting in LPTENUM\Sample_Printer_CompaAAA2.
For another parallel port device to report itself as compatible with the device described in this INF file entry, it must report a CID keyword value of
LPTENUM\Sample_Printer_CompaAAA2
If the INF file entry had the alternate form of
"Sample Printer"=X.DRV,LPTENUM\Sample_Printer_CompaAAA2, Sample_Printer_CompaAAA2
then the device could alternately report itself as
Sample_Printer_CompaAAA2
Note that the very first time Windows 95 is started on a computer, the way CID values are handled differs from the way they are handled for all subsequent start ups. For more information, see the section Ordering of Device ID and Compatible Device ID Values.
A printer which is compatible with the HP LaserJet 4L, and for which the vendor has the necessary rights to use a driver provided by another vendor, returns the following CID key value:
LPTENUM\Hewlett-PackardLaserC029
In order to use this CID value, you must have legal rights to install the printer driver provided by the other vendor (in this example case, Hewlett-Packard).
A printer which is compatible with the HP LaserJet 4L and which uses the driver provided by Microsoft returns the following CID key value:
HP_LaserJet_4L