*About* – Displays a *NextZXOS About* screen with several credits to contributors of bug reports and suggested features. The *NMI menu,* uses the familiar *Browser* interface *dialogs* for loading and saving of files as needed as can be seen in the next figure. ### The NextZXOS folder structure To achieve a *complete* and properly booting *NextZXOS* the following folders and files need to be present on an SD Card: At the root level there's the *Firmware* file (**TBBLUE.FW**) and the folders **c:/nextzxos/** carrying all the drivers (*RTC*, *Mouse* etc), support programs and overlay files as well as the base *CP/M* image file together with the startup command file **autoexec.bas**. Then there is **c:/machines/next/** which contains two versions of the *NextZXOS* ROM (they differ in the type of 48K ROM they contain; *Sinclair* or *Looking Glass*), the *NextZXOS divMMC* ROM, the *NMI* ROM as well as the configuration file **config.ini** which tells the *Firmware* the particular settings you require for your machine. Finally, there is **c:/dot/** which contains, apart from the third party *dot commands*, the ones that constitute part of *NextZXOS,* namely: **.$**, **.bas2txt**, **.browse**, **.browseprefs**, **.cpm**, **.defrag**, **.editprefs,** **.guide**, **.install**, **.lfn**, .mem, **.mkdata**, **.mkswap**, **.nextver**, **.txt2bas,** **.uninstall** and **.unzip**. To obtain just a booting *NextZXOS* you do not need the *dot commands*, *CP/M* base image, *mouse driver, RTC driver* or even **autoexec.bas** and *NMI* rom. Your functionality however will be limited. ### NextZXOS dot commands We have talked about *dot commands*, covering each one as the case dictated, but we haven't talked about what they actually are! Well, dot commands are basically an easy way to add functionality to *NextBASIC* (and ZX BASIC) originally invented for use by *esxDOS* by its author, Miguel Guerreiro. Copying from the *z88dk*[^p199-19] documentation by Allen Albright: *A dot command is loaded into an 8 K ram page located at address 0x2000, overlapping the rom, and can run without disturbing the basic system. They are launched from basic by typing their names with a leading dot, hence the name "dot command". Any string following the dot command's name is passed as a command line. On return the dot command can generate esxdos errors in the basic system, either canned ones or custom ones.* *NextZXOS* has extended the scheme while remaining compatible with the original specification, thus a separate set of *dot commands* is included with **System/Next™**, than what comes with *esxDOS*. See the *esxDOS* section below for more details on the differences. The scope of this manual is a bit limited to cover *dot commands* in their entirety but you can visit: **https://github.com/z88dk/z88dk/tree/master/libsrc/_DEVELOPMENT/EXAMPLES/zxn/dot-command** to find out more about how they work and how you can write your own. *NextZXOS*, apart from the third party ones included in the **System/Next™** distribution, has several *dot commands* that perform special functions not covered elsewhere. These are: **.$** *Dot commands* cannot accept string arguments from *NextBASIC*, so **.$** allows execution of a *dot command* accepting any parameter passed as a string thus enabling full integration of *dot commands* in *NextBASIC* **.bas2txt** and **.txt2bas** *NextBASIC* is stored in a *tokenised* form. That means that each keyword occupies one token (see *Appendix A* for these values). [^p199-19]: *z88dk is a C-based cross-development system for a variety of Z80 compatible CPUs and systems.*