April/May 1980 · Issue 7

Page 32 of 39

PI This gives the value of PI

INCH This waits for an input character. This is extremely useful in many programs.

KBD Checks for an input character and returns the value 0 if there was no input. This makes it easy to write games programs where fast reactions are required, and has many other uses.

ON ERR GOTO or GOSUB This is a remarkable addition to the Basic, and allows any error during execution to be trapped and the appropriate action taken. The variable ERR supplies the number of the error, and the CMD$ function gives a full text description of the error.

The XTAL Basic has another astonishing feature which is extremely useful. You can add your own commands to the Basic, specifying the name of the command, and the address at which you have stored the machine code. This means that it would be easy for those familiar with machine code to add the Nascom Basic commands which have been omitted from the XTAL Basic. In fact the manual supplied gives the code for the addition of DEEK and DOKE commands as an example. Another feature is the backspace key allows one Basic statement to be executed at a time, which is useful for debugging.

The XTAL Basic does not have the Nascom Basic WIDTH command, which surprisingly, is an improvement, as the Nascom Basic command has the annoying habit of putting out carriage returns when you don’t want them. DEEK, DOKE, and the graphics commands, SET, RESET and POINT are also missing, but with the ability to extend the command table, could easily be added.


The XTAL Basic is a good Basic with several useful enhancements to the arbitary standard ‘8K Basic’. It is not compatible with Nascom Basic, but the missing commands could be added. It would be better if it used the NAS-SYS editing, but still had its own EDIT command, which had advantages for long lines, using the cursor movement keys in the standard way.

Cost and availability

If you already have version 2.1 XTAL Basic, send your tape back with 50p, and Crystal will send you the new version. Otherwise, XTAL Basic is available for 35.00 + VAT from :

Crystal Electronics,
__, _________ ____,
Torquay, Devon.
(Tel. ____ _____)

Page 32 of 39