INTERVIEWER: What do you consider your greatest achievement ever in programming?

GATES: I’d have to say BASIC for the 8080, because of the effect it’s had, and because of how appropriate it was at the time, and because we managed to get it so small. It was the original program we wrote when we decided to start Microsoft.
Three of us knew that original program by heart. We got a chance to completely rewrite it one summer down in Albuquerque, and I thought we could save a few bytes and tighten things up. We just tuned the program very, very carefully, and ended up with a 4K BASIC interpreter.
When you know a program that well, you feel that nobody can look at the code and say, “There’s a better way to do this.” That feeling’s really nice, and the fact that the program was used on a lot of machines makes it an exciting program to have written.
I also feel really good about the software on the Model 100, especially about how we squeezed in a very useful small editor. I worked with Jey Suzuki, a Japanese programmer, to put that together. We had very limited time to finish the project. When you do software that gets burned into ROM, you don’t get an opportunity to make mistakes.