This week, we learned that Dr. Dobb's Journal is shutting down after 38 years. Admittedly, I haven't paid much attention to Dr. Dobb's for the past few years, but back when I was a kid who wanted to be a programmer, I anxiously awaited each monthly issue so that I could read every single article multiple times. We didn't have the Internet to give us whatever training we needed whenever we wanted, so magazines like Dr. Dobb's were precious.
While reminiscing about Dr. Dobb's with other grieving Twitter users, somebody brought up the fact that the first issue was titled "Dr. Dobb's Journal of Tiny BASIC Calisthenics & Orthodontia: Running Light Without Overbyte" (which I think is the coolest magazine title I've ever heard). It started as a xerographed newsletter to tell people about Tiny BASIC, a simplified BASIC programming language interpreter that could run in 2 or 3 kilobytes of memory. That was an important feature back when personal computers had only 4 kilobytes of memory.
Having just completed an implementation of a Forth programming language interpreter in Apple's new Swift programming language, I got the idea of implementing a Tiny BASIC interpreter in Swift. It didn't make any sense. I didn't want to write any programs in Tiny BASIC. I didn't think anybody else would want to write any programs in Tiny BASIC. There are more important things I could be doing with my free time.
But, apparently, reimplementing 50-year-old programming languages in Swift is my thing now
I did it. I call it "Finch", and if you want it, you can find it here:
- https://github.com/kristopherjohnson/FinchBasic
Useless as it may be, it was an interesting exercise. Most of the Tiny BASIC implementations you find are focused on the original goal: getting a full implementation to fit in a few kilobytes. That isn't an important goal anymore, but I liked the idea of implementing a very-simple programming language. I focused on these goals:
- Use Swift's high-level abstraction features, rather than writing code that looks like C or assembly language.
- Make it easy for new Swift programmers to understand, so it could be useful as a beginner's example or in a tutorial.
- Make it easy for people to hack on to add new features.
I think I did alright. It's about a thousand lines of code (not counting blank lines and comments), which is smaller than a C-based Tiny BASIC implementation I found, and I don't think I did anything too complicated. I will have to wait and see if anyone else wants to hack on it.
BASIC was the first programming language I learned. I expressed an interest in programming after attending an IBM open house, and my father brought home a BASIC programming manual. I studied it intently, but there weren't any computers around, so it was a while before I could try out what I had learned. But eventually the Radio Shack at the local mall started selling the TRS-80, and I could walk into that store and write my very first program:
10 PRINT "TRS-80 SUCKS! ";
20 GOTO 10
RUN
With great power comes great responsibility.