ent numbers) and each *partition* on each *disk* (if a *partition* exists) is assigned a number in turn. *Virtual disks* on the other hand do not have device numbers as they don't physically exist however both require a *driver*; that is a small program that sits between the *disk* and *NextZXOS* and translates each device's individual characteristics into the common set of controls that *NextZXOS* understands. That alone however is not enough; *NextZXOS* needs to assign a *drive* to each *partition* on a *disk* (or in the cases of *virtual disks* and the *RAMdisk* to the *disk* itself). As it comes with your **System/Next™** distribution; *NextZXOS* knows three types of *physical disks*: *SD Cards*, the *RAMdisk* and *floppy disks* and two types of *virtual disks*: +3 *floppy disk images* and *IDEDOS hard disk images*. It also knows *virtual* and *physical tapes* both addressable via the reserved drive **t:**. *Physical disk* device numbers start at **0** and are assigned according to the table that follows: | Device Number | Description | |---|---| | 0 | All IDEDOS partitions on the first SD drive | | 1 | All IDEDOS partitions on the second SD drive | | 2 | Reserved for First Floppy Disk drive | | 3 | Reserved for Second Floppy Disk drive | | 4 | RAMdisk | | 5 | All FAT partitions on the first SD drive | | 6 | All FAT partitions on the second SD drive | *Table 15 – Device Number assignments* On an unexpanded ZX Spectrum Next with an unmodified distribution of *NextZXOS*, the first used number is **4** which is the *RAMdisk* and the second is **5** as **System/Next™** comes on an SD card containing only a single *FAT partition*. As seen on the table above, device numbers **2** and **3** refer to floppy disk drives (not yet supported by *NextZXOS*). #### Mounting In order for *NextZXOS* and *NextBASIC* to know how to access a *partition* or *disk* (be it *physical* or *virtual*) this *partition/disk* has to be *mounted*. That is the process where a *partition* on a *device* gets attached to a *drive*. If freshly installed, *NextZXOS* will automatically mount two drives; drives **c:** and **m:** the first being device **5** partition **1** (in other words the **System/Next™** distribution's SD card plugged into the first SD reader of the system) and the second one being device **4** (the *RAMdisk*). On an initialised *CP/M* distribution (as we'll see further below) one more drive will be mounted and that's drive **a:** (assigned to **cpm-a.p3d** located inside **c:/nextzxos/**). Generally speaking, if there are more than one *FAT partitions* detected on the SD card(s), they will be automatically mapped to drives **c:** onwards on startup. Finally, any files located inside the **c:/nextzxos/** directory, are mapped to the appropriate *drives* (if the *drive* in question has not already been mapped), if they are named as follows and are valid *+3DOS partition images*: **DRV-A.P3D**\ **DRV-B.P3D**\ (…)\ **DRV-P.P3D**\ **CPM-A.P3D**\ **CPM-B.P3D**\ (…)\ **CPM-P.P3D** *Virtual images* named **DRV-x.P3D** (where **x** is a letter from **a** to **p**) have preference over *virtual images* named **CPM-x.P3D** so in the presence of both, the **DRV-x** variant will be mounted. Apart from the *auto-mounting* procedures described above; we can also manually *mount partitions* and *disks*. This will be covered a bit further below at its own section.