00: Introduction

Most of the things you do with a computer are related to processing inputs. If you're dealing with files, then you're usually processing text or binary data in a similar way. If you're opening an image file, then you're doing some kind of input processing. Want to convert a CSV file to Excel? That's going to require processing the CSV. Even if it's not a data file you're still doing some kind of input process. The text you type into your browser window to access a website and even the mouse clicks require some form of input processing.

Another term for "input processing" is parsing. Parsing text involves creating a logical piece of software that understands the structure of the input, and organizes it into an internal structure so you can work on it. When you read that CSV file you are parsing it because you create rules that say things like, "When I see a comma, do this, and when I see a number, do that." Whether people realize it or not, a ton of software is mostly just parsing inputs, even if those inputs aren't text.

You can extend the concepts in parsing to so many things in computer science that it becomes one of the central components of computation. Need to control the state of a User Interface when a user clicks around with a mouse randomly? Parsing. Need to organize the data packets that a server receives so they make sense? Parsing. Need to convert a stream of telemetry data into a meaningful log? Parsing. The techniques in parsing are literally found everywhere in computer science.

And, the first step to understanding parsing is to learn about regular expressions. You can "get by" without them, but learning regex teaches you the first baby steps of parsing. If you can learn how regex work, then the rest of parsing is effectively just higher level regex.