Better than FORTRAN

Sniffles and sneezes kept me home. I spent most of the day resting. Yet I had a little time to build an interpreter for the original BASIC language, and I learned a lot.

Writing an interpreter (or a compiler) forces one to learn the language. All of the language, not just the convenient bits. My exercise forced me to learn about BASIC and think like the original designers of the language.

I looked at the original BASIC, also called "Dartmouth BASIC". It is a simpler version of the Visual Basic we know today. There is a limited command set and variable names are much shorter.

I implemented a fraction of Dartmouth BASIC. I'm calling my implementation "BASIC-1965", in reference to the year in which I think it would have been initially implemented. It is Dartmouth BASIC without the matrix operations and constraints on the use of expressions. In Dartmouth BASIC, expressions may appear in LET, PRINT, FOR, and IF statements; in my version, expressions are restricted to the LET command. (That may change in the near future.)

Another change is the position of DATA statements. In the original BASIC, DATA statements may appear anywhere. In my "BASIC-1965", DATA statements are truly interpreted and must appear prior to the corresponding READ statements. (The fact that DATA statements could appear at the bottom of the program always bothered me.)

My implementation is in Ruby, which performs a lot of the "heavy lifting". Ruby has data containers and regular expressions, both of which made the task easy.

I can see how BASIC was better than FORTRAN: no FORMAT statements, no worries about integer or floating point variables, and interaction with the computer. It *was* a significant increase in usability.