Modifications To Tiny BASIC For NAS-SYS

By Buxton

This article is intended to show how the Tiny Basic Interpreter –V2, published the Merseyside Nascom Users Group program book, can be changed to run under Nas-Sys 1/3, rather than under monitor T4 for which it was originally intended. In addition, the modification provide full screen editing of the source text. Assuming that a copy of the interpreter is in store, all that is required is to change the locations specified below to the new code, replace the old editor routine at £17C5 with the GETLN routine given in the full assembler listing, then save the new version of Tiny Basic on tape. Please note that old programs written for TBI-V2 will have to be altered, since the end of line marker is now £0D, rather than the £1F used by T4 and the earlier monitors. Other changes are:

1. The command separator is now ‘:’ rather than ‘ ;’
2. Format control in print now takes the form [5 if you wish the number to be printed in 5 spaces
3. ‘CLEAR’ is no longer active
4. The ‘DUMP’ command is replaced by ‘SAVE’
5. Any number preceded by £ is now hexadecimal which makes POKEs very much easier. This may be used anywhere, e.g. FOR X = £C to £FF
6. When reading a tape you must first poke the ASCII code for the letter R, £52 or 82 decimal, into ARGX in the workspace (£C0B, 3083), or the tape will be verified, not Read
7. If you are using Nas-Sys 3 you must also poke a zero into location ARGN (£C2B, 3115), or the program may be loaded at the wrong location.
8. The input function X = IN (port no.) becomes X=CODE(£14AC)(port no.)

I hope that these notes and the list of modifications will prove useful to everyone who has asked for an updated version of TBI-V2.