The Evolution of Programming Languages

A programming language is a systematic notation by which we describe computational processes to others. By a computational process I mean nothing more than a set of steps which a machine can perform for solving a task. To describe the solution of a problem to a computer, we need to know a set of commands that the computer can understand and execute. Given the diversity of tasks that computers can do today, people naturally find it surprising that the computer’s built-in abilities are so primitive. When a computer comes off the assembly line, it will usually be able to do only arithmetic and logical operations, input and output, and some “control” functions. These capabilities constitute the machine language of the computer. But because this language is so far away from the way people think and want to describe solutions to problems, so-called high-level programming languages have been conceived. These languages use less primitive notations than machine language and hence they require a program which will interpret their meaning to the computer. This program is not generally part of the computer’s circuitry, but is provided as part of the system software which is included with the computer. The purpose of this book is to study how these programming languages are designed to meet the needs of the human and the machine.