# Programming Concepts

> The ideas under every language - how code runs, data structures, async, memory, big-O, and choosing the right tool.

13 guides.

- [Programming From Zero](https://themissingmanual.dev/guides/programming-from-zero) _(beginner)_ - What a program actually is, the building blocks every language shares (variables, types, operators), and how code makes decisions and reuses work with if/else, loops, and functions.
- [What Actually Happens When Your Code Runs](https://themissingmanual.dev/guides/what-happens-when-code-runs) _(beginner)_ - The journey from the text you type to a living program: how source code gets translated into machine instructions, where your data lives while it runs, and what 'running' actually means to the operating system and CPU.
- [Regular Expressions, Explained](https://themissingmanual.dev/guides/regular-expressions-explained) _(beginner)_ - A regex is a pattern that describes the shape of text - not code you run, but text you describe. Learn the mental model, the small toolkit you'll use 90% of the time, and how to avoid the classic traps.
- [Async/Await & the Event Loop](https://themissingmanual.dev/guides/async-await-and-the-event-loop) _(intermediate)_ - Async exists because programs spend most of their time waiting; the event loop is a single thread plus a queue of ready-to-continue work; and async/await is just readable syntax over 'a value that isn't here yet.'
- [Memory & Garbage Collection, Explained](https://themissingmanual.dev/guides/memory-and-garbage-collection) _(intermediate)_ - What actually happens to the objects your code creates: where they live in memory, why some of them have to be cleaned up, and how the two big approaches - freeing memory by hand versus a garbage collector that does it for you - really work.
- [Python, JavaScript, Go & Rust - Explained Like a Human](https://themissingmanual.dev/guides/languages-explained-like-a-human) _(beginner)_ - What each major language is actually for and what it feels like to use, so you can choose one on purpose instead of by hype - the axes that make languages different, a clear-eyed look at four of them, and a practical way to pick.
- [Object-Oriented vs Functional, Plainly](https://themissingmanual.dev/guides/oop-vs-functional) _(intermediate)_ - Two ways of organizing code, demystified: what object-oriented programming actually is, what functional programming actually is, and the plain truth about which to reach for and when.
- [Dates and Time Zones](https://themissingmanual.dev/guides/dates-and-time-zones) _(intermediate)_ - The bug that corrupts data and breaks launches: UTC versus local, offsets versus zones, DST, and the rules that keep time from wrecking your app.
- [Character Encodings and Unicode](https://themissingmanual.dev/guides/character-encodings-unicode) _(intermediate)_ - Why text turns into garbled symbols, how UTF-8 actually works, and the difference between bytes, code points, and the characters a user sees.
- [Floating Point and Money](https://themissingmanual.dev/guides/floating-point-and-money) _(beginner)_ - Why 0.1 plus 0.2 is not 0.3, what floats can and cannot represent, and the iron rule: never store money in a float.
- [Closures and Scope](https://themissingmanual.dev/guides/closures-and-scope) _(intermediate)_ - Why a function remembers variables from where it was born: scope, closures, and the captured-variable bugs that bite in every language with first-class functions.
- [Pointers and References](https://themissingmanual.dev/guides/pointers-and-references) _(intermediate)_ - A pointer or reference is a variable holding a memory address instead of a value - the idea underneath sharing, mutation, and half the bugs that make you say 'but I didn't touch that variable.'
- [How Garbage Collectors Actually Work](https://themissingmanual.dev/guides/how-garbage-collectors-work) _(advanced)_ - The engineering deep dive behind automatic memory management: reference counting vs. mark-and-sweep, why generational and concurrent collectors exist, and how to read a real GC log and tune the knobs that matter.