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Ian Cull
Chris Bourne


IMBOS or ExBasic? Now that is the question!

Having finally got my hands on the new microdrive program, I must report that the IMBOS saga has developed a new twist. The original IMBOS V1.1, is still available from the author (Companion Software), but a new version IMBOS V2, is now available from Kobrahsoft (the company that brought +3 users the DICE program - Issue 57). But what is IMBOS I hear you cry. Well actually the title stands for Improved Microdrive Basic Operating System, and the program is obviously only of use to Spectrum owners that have the Interface One & microdrive system. For these people, upwards of 60 new facilities are added to the Spectrum, in 11K of code (8K if you purchase the old version, 1.1).

The first apparent facility of IMBOS is the vastly improved microdrive command syntax. No more LOAD *"m";1;"filename" entries. Just type RUN "filename" to load a program (also works for CODE and SCREEN$ files), or OUT !"filename" to save. VERIFY and ERASE are similarly simplified. The microdrive number that these commands use is set by READ #x.

A new command, LIST CAT x, gives a different microdrive catalogue, showing protected filenames as well as those shown by the normal CAT. There is also a header reader, accessed by typing READ IN "filename". The file's type, and size/start address are given, along with the first sector number of the cartridge.

IMBOS also adds new screen and sound commands, as well as additional graphics routines, The PRINT command is expanded to allow conversion between hexadecimal and decimal (for example, PRINT &64206 prints FACE on screen). Screen paper and ink colours can also be simply altered, using PRINT ATTR x.

Other new functions allow specified byte values in the display or attribute file to be changed (this could be used to instantly change the colour of a displayed picture).

Printing of text is improved with a centring function, and a 'window scroll' routine. There is also a double-height print command, for displaying tall characters (not available on V1.1).

On the graphic front, mirroring of the screen is built in (although it mirrors each character wide column, rather than the full screen), and a powerful fill routine is available. New character fonts can be easily defined, since the full character set is held in RAM along with IMBOS - in fact a clear font is supplied on the tape, ready for loading into IMBOS.

Version 2 also offers a 'power plot', which allows drawing on the full screen - including the edit window, and a DRAW command which takes the start & end coordinate as argument, and also works over the full screen (but the origin is at top-left, which is confusing, and gives upside-down graph plots). Also on offer are scroll commands, for the display file or the attributes, in all four directions.

Sound is well catered for, offering White Noise, Zap and Siren sounds. Version 2 has more Zaps, and a pleasant tone, for music sequences.

Other IMBOS features include a RAM screen store routine (though it is not a compacting one, so only three screens could be held in a 48K memory at once), and a pseudo- 16-bit poke function. *DOKE. Headerless save/load routines are present, as well as various monitor commands, including some to give details of memory usage (program size, free space etc). Version 2 also offers a program editing command (so all LPRINT commands could be automatically changed to PRINT ones), and an additional Organ Maker program, for creating tune sequences to be added to your own programs (which I found difficult to use).

In conclusion, IMBOS is a powerful addition to any Spectrum and Interface One set-up, enabling BASIC to do many things that normally require machine code. However, since IMBOS is copyrighted, you could not write a program with it and sell it, or even give a copy to your friends (unless they also own IMBOS).

Despite this, and a couple of minor bugs/annoyances (commands are not recognised if keyed in lower case, for example), the program is worth buying for the sheer expansion of microdrive syntax. IMBOS Version 2 is available from Kobrahsoft, Pleasant View, Hulme Lane, Hulme Near Longton, STOKE-ON-TRENT, Staffs ST3 5HB for £12.95. Owners of IMBOS V1.1 wishing to upgrade can do so, for £5.95. Version 1.1 is still available at £8.95 from Companion Software (address elsewhere). Microdriveless Spectrum owners read on...

Screenshot Text

'The vastly improved microdrive command syntax'

'Mirroring of the screen is built-in'

'The origin is at top-left... and gives upside-down graph plots'