This is an attempt to summarize some of the basic ideas behind programming languages. It was originally written for "people who know one language and are wondering about learning another", and hasn't strayed far from that aim.

It is not a detailed, scholarly exploration of all programming languages, nor does it describe the latest developments (or even cover all the basics) in computer science - I simply do not know enough to attempt that. Instead, I have tried to write something that is clear, unbiased, and useful to someone with no knowledge of the theory of computing.   More detail...