IT Foundations

A free course for anyone who has started building programs and apps and gets stuck on terms like server, API, deployment, and environment variable. Instead of writing code, you check what each piece does and how it works through diagrams, so that you can put the steps and explanations in books and courses into your own words. No runtime environment is used.

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IT Foundations

What a Program Is — How It Relates to CPU, Memory, and Storage
Saving and running are separate events. Starting from the fact that a program is a sequence of instructions, and from how the CPU, memory, and storage divide the work, this article explains why saving a file is not enough to run it.
Where Your Code Runs — Browser, Server, and Phone Apps
When you want an app to work on phones as well, you have to choose between a web app and a native app. This article works through that difference using the three places code runs (the browser, the server, and the phone's OS) and the difference between running on your computer and running once it is published.
The Parts of a System — What You Build In-House and What You Hand to External Services
This article works through the four parts that make up a web application, why external services are the one part you use through an API instead of building it yourself, and how each part succeeds or fails independently.
How Programming Languages Differ, and What Frameworks and Libraries Are
When you are deciding whether to learn Python or JavaScript, or wondering whether Next.js is a language, you need to know how programming languages differ and how libraries and frameworks relate to your own code. This article covers both.
What a Development Environment Is — Editor, Terminal, and Runtime
So that "open a terminal" in a set of steps no longer stops you, this article covers what the editor, the terminal, and the runtime each do, and what happens between typing one line and having it run, checking each step as you type the commands yourself.
What Package Management Is — What npm install Installs, and Where
So that "run npm install" in a set of steps no longer stops you, this article covers what a package is and what appears inside my-app once you run it, by following how the contents of the folder change.
What Git Is — Recording Changes So You Can Go Back
So that you can return to an earlier state when an edit stops your code from running, this article works through the difference between saving over a file and committing, the two stages of choosing which changes to record, and how a repository relates to a remote repository.
How Networks Work — How Data Reaches the Right Destination
What a network does is deliver data to the right destination. Using a network diagram, this article works through how a LAN and the Internet nest inside each other, how the destination IP address decides which path the data takes, and the router and default gateway that sit at the boundary.
What Happens When You Enter a URL — DNS, HTTP, and HTTPS
This article explains what the http://localhost:3000 in a set of steps points to, using the four parts of a URL and the DNS, HTTP, and HTTPS flow that runs from entering a URL to the page appearing.
The Three-Tier Web Model — Dividing Work Across Web, Application, and Database
So that the explanation "separate the frontend and the backend" no longer stops you, this article works through why a web app is split into three tiers — web, application, and database — and how data flows across them.
The Differences Between HTML, CSS, and JavaScript — What the Web Server Tier Draws
This article works through which part of the screen HTML, CSS, and JavaScript each decide, how the three files connect through class and id, and how the browser builds a DOM from HTML and draws it.
Server, Serverless, and Container — The Application Server Tier
This article compares an always-on server with serverless by how long the processing program is running, how you add capacity when requests increase, and what you have to provide yourself, and then covers where containers fit.
What a Database Is — How It Differs from a File, Tables, and SQL
This article works through why bookings are stored in a database rather than a file, using the shape of a table made of rows and columns, where SQL fits as the way you tell the database to read and write, and the three stages of the steps in introductory books.
What Is an API — The Agreed Rules Programs Use to Exchange Data, and JSON
This article explains why a weather display is described as "calling a weather API," using the three elements of an API call — URL, method, and response — and how to read the keys and values in the JSON that comes back.
API Keys and External Services — What a Key Protects, and Webhooks
This article works through what "get an API key and put it in .env" means, covering how a key is a string that identifies who is making the call, and the webhook flow in which the external service calls your own server.
Cloud vs. On-Premises — Shared Hosting and Scope of Responsibility
This article compares on-premises, shared hosting, and the cloud by where the server hardware sits and how far up the layers you manage yourself, and shows that AWS, Google Cloud, and Azure offer the same categories of service under different names.
Deployment and Environment Variables — From Working Locally to Going Live
This article explains why an app that worked on your computer does not work once it is published, using the three stages of deployment — build, place, and publish — and how environment variables switch the values that differ between development and production.
Custom Domains and Certificates — Putting Your Own Name on a Published URL
This article works through replacing the long URL you were assigned automatically with your own domain and making it open over https, split into three parts: registering the domain, DNS records, and the server certificate.
You Fixed It but the Screen Has Not Changed — How Caching Works
This article works through why the browser still shows the old page after a fix, using the three places old copies are kept, how to tell whether it is only you or everyone, and how to use file names to make sure the new file is delivered.
Security Points to Watch — Do Not Trust Input, Protect Secrets
This article works through the principle of not trusting user input, using server-side validation, SQL injection, and XSS, then covers where you may and may not keep secrets such as API keys and passwords, in terms of environment variables and .env.
How Login Works — Authentication, Sessions, and Cookies
This article works through the difference between authentication and authorization that appears in explanations of login, why passwords are stored as hashes, how sessions and cookies let the server know it is the same person after login, and how the session approach differs from JWT.
How Billing Works — What Stripe Handles, and Granting Entitlements by Webhook
This article works through the payment provider and the webhooks that come up when you add a paid plan, using the mechanism that keeps card details from passing through your own server and the flow from receiving a payment to granting the user access.
How to Read Errors and Logs — Where to Look and What to Report
This article works through where to look when all you can say is "I got an error," using the structure of an error message and a stack trace, how to read the logs that record what happened, and the four pieces of information to include when you ask.