Back in the day, one of the coolest things to do with a personal computer was to get a BASIC interpreter running so “anyone” could write programs. If you’re a doubter/hater of BASIC, bear in mind that Dr Dobb’s Journal started as a way to get tiny BASIC interpreters running on early processors! It’s not a great language, but was fun back then and is still fun now.
This is a collection of BASIC interpreters that I’ve found on the net, sometimes with source, sometimes with some of my enhancements. Please note that I did not write any of the BASICs here, and only modified some of the code very slightly.
Technical Systems Consultants (TSC) Micro BASIC Plus
This is a small BASIC that only has integer math, limited functions, and limited variables. However, it was one of the earliest BASICs for the SWTPC.
Step-by-Step Instructions
Download MicroBas.zip which contains the source, listing, and an S19 format file:
This is easy to load and run:
$L <send the MicroBas.s19 file… not too large>
$J 0100
Source Code
The source code is part of the previous zip file and is on the net, so I simply converted it to my assembler’s syntax, added conditional assembly of the I/O driver, and fixed one bug in the numeric output subroutine.
Microsoft 8K BASIC
This is a really good one and includes floating point math. Details are on one of Michael Holley’s pages. Everything here is originally from his site. Getting a Tiny BASIC running was great, but the ultimate goal for most people was to get MS BASIC because it was becoming the de-facto standard and had a lot of software written for it. It also had floating point, nice string handling, and other goodies.
Step-by-Step Instructions
Download msbasic.zip, unzip it, which will produce both msbasic.s19 and mspatch.s19:
Now, to load BASIC, you need to download the original MITS file first, then the patch:
$L <download msbasic.s19… it’s big>
$L <download mspatch.s19… very small>
$J 0000
By the way, there is a well-known Easter egg in Microsoft BASIC. When it asks for memory size, answer A and get the author:
Source Code
I have not seen a disassembled version of the 6800 BASIC, so all I can offer is my slightly modified version of Michael’s driver. MS BASIC sets the MSB of the last bit of text messages, so I took Michael’s original driver, moved it a bit higher in memory since our boards have RAM at A080, and cleared the MSB on the output function.
<mspatch.asm>
BASIC Games
While looking at my collection of old computer magazines for some vintage software, I remembered David Ahl’s two books of BASIC computer games and found used ones for cheap on Amazon. Then I realized at least one book is entirely on-line:
Not all of them run on every BASIC interpreter, but you’ll have the best luck with the 8K Microsoft BASIC, as Microsoft was quickly establishing itself as the standard BASIC back then.