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networks/ip-addresses-and-ports-the-street-address-and-the-apartment-number.md IP addresses and ports: the street address and the apartment number Every message on a network needs two things to arrive: an IP address to find the right computer, and a port to find the right program on… 10 min read · 1 Oct web/html-tags-how-angle-brackets-become-a-tree-in-your-browser.md HTML tags: how angle brackets become a tree in your browser Every web page is plain text with labels in angle brackets: HTML tags. An opening tag, some content and a closing tag make an element, and… 13 min read · 1 Oct tools/git-basics-where-your-work-lives-and-why-branches-are-just-pointers.md Git Basics: Where Your Work Lives and Why Branches Are Just Pointers Git saves your project's history as commits: snapshots you choose to take, each with a short message. The trick to understanding it is… 10 min read · 1 Oct software-design/functions-why-you-should-stop-copy-pasting-your-code.md Functions: Why You Should Stop Copy-Pasting Your Code Copy-pasting code works fine on the day you do it. It fails the day you need to change it, and have to find and fix every copy without… 9 min read · 1 Oct databases/your-first-sql-query-ask-a-table-of-pets-a-question.md Your first SQL query: ask a table of pets a question SQL is the language you use to ask a database questions, and five words get you surprisingly far: SELECT, FROM, WHERE, ORDER BY and LIMIT… 9 min read · 1 Oct networks/how-does-example-com-turn-into-an-ip-address-dns-step-by-step.md How does example.com turn into an IP address? DNS, step by step Computers find each other by number, not by name. Before your browser can load example.com, it has to find the site's IP address, and… 11 min read · 1 Oct databases/why-databases-split-your-data-into-two-tables-and-link-them-by-id.md Why databases split your data into two tables (and link them by id) A database table looks like a spreadsheet: columns for each kind of information, one row per thing. But it comes with rules. Every column… 10 min read · 1 Oct web/why-your-200px-box-is-250px-wide-the-css-box-model.md Why your 200px box is 250px wide: the CSS box model Every element on a web page is a box made of four layers: content, padding, border and margin. By default, CSS width measures only the… 8 min read · 1 Oct ai/how-a-chatbot-writes-one-guessed-word-at-a-time.md How a chatbot writes: one guessed word at a time A chatbot doesn't plan its reply and then type it out. It repeats one small step: look at the text so far, give every possible next token… 12 min read · 1 Oct computers/counting-with-only-0-and-1-how-computers-store-numbers-and-letters.md Counting with Only 0 and 1: How Computers Store Numbers and Letters Every photo, message and web page on your computer is stored as numbers written with just two digits: 0 and 1. That's binary, and it works… 9 min read · 1 Oct mobile/why-does-your-phone-ask-allow-this-app-app-permissions-explained.md Why does your phone ask "Allow this app?" App permissions explained Every app on your phone lives in its own sandbox: free to use its own files, but walled off from other apps and from personal things like… 18 min read · 1 Oct languages/what-a-variable-really-is-python-names-values-and-the-sign.md What a variable really is: Python names, values and the = sign In Python, a variable isn't a box that holds a value. It's a name tag tied to a value that lives on its own. That one picture explains why… 7 min read · 1 Oct