the *esxDOS-compatible API*) which can be used from *machine-code* or a language other than *NextBASIC* (for example *C*) to provide them with all the facilities needed for accessing your ZX Spectrum Next without having to write *low-level* access to the computer's hardware from scratch. The distinction is subtle and more easily discernible in facilities that are exposed to the 48K legacy mode of operation where the *NextBASIC* commands do not exist and their place is taken by the aforementioned *dot commands*. In the following sections we will examine the *NextBASIC* usage of *NextZXOS* facilities before we extend the discussion to *dot commands* and the *NextZXOS Command line so for the next few sections you can approach the subject as a NextBASIC* topic if you feel more comfortable that way. Let's however start by introducing topics in the order they will be needed in our discussion. > **Notes** > > In this chapter, a lot of commands produce visual feedback that may be easier to see and understand on a 64 or 85 column display. Although *NextZXOS* menus are covered much later in the chapter, it may be of benefit to learn to use the *Command Line* in combination with the *32/64/85* option. You get to the *Command Line menu* either from the main *NextZXOS menu* or by pressing **EDIT** and navigating to it while in *NextBASIC*. Pressing **EDIT** again will allow you to select the *32/64/85* option which will cycle through all available widths until you find one that visually satisfies you. ### Files, Drives, Partitions and Disks Like most Operating Systems, *NextZXOS* uses the concept of *Files* to store data in a hierarchical organised set called a *Drive* identifiable by a *Drive Name*. This is the combination of a letter[^p158-5] from **A** to **P** suffixed by a colon ie. **d:**, which in turn can be contained within a *Disk*. A *file* is any type of collection of data; *Sprites, Arrays, NextBASIC programs, machine code, images* or collections of the above. While *NextZXOS* via *NextBASIC* supports a finite set of file types, this set can be extended with the use of external programs and *dot commands*. For the following sections we will concentrate to what is available via *NextBASIC* and the provided *dot commands* with a brief discussion of how *NextZXOS* (and *NextBASIC* in turn) can be extended to handle more file types. *Files* are usually organised in *folders*. While *folders* are not necessary for the storage of *files*, they are advisable as they help categorise and group *files* in a logical way, which allows them to be searched and accessed easily. That becomes apparent as your collection of *files* grows from a few tens to hundreds or thousands. As mentioned above, *files* themselves are stored on *disks*, which are the physical *devices* that can be removed from the computer and whose contents are not lost like the main memory after each power cycle. Depending on the type of *disk*, there may be one or more data structures on it called *partitions* which as the name implies is a way to virtually organise the available space on the *disk* into smaller units. *Partitions* can be assigned to *drives* or sit unused –with or without data– invisible to *NextZXOS* (until a *drive* is assigned to them). Apart from the *physical disks*, *NextZXOS* also allows the use of *virtual disks* and *tape images*. These are special files that contain an exact replica of the medium they simulate. They too, can be assigned to drives (see the footnote regarding tape images) as physical disks can and they appear to the user (and *NextBASIC*) as any other physical disk. There are some special considerations regarding these special files which we will visit further in this chapter. ### Working with files In our examples in the previous chapters we have already used *files* and specifically one particular type of file: *NextBASIC* programs. Even more specifically, we have **SAVE**d and **LOAD**ed them by using two commands: **SAVE** and **LOAD**. [^p158-5]: *NextZXOS* cannot assign all letters in the range A to P as drives, since some are reserved; **C:** is always the boot drive, **M:** is the RAMdisk and **T: (an exception to the A to P range)** is the tape.