Lesson 1: Layers of Abstraction — The Big Map
A computer looks like magic: you tap an icon and an app opens. But there is no magic — there is a tower of abstraction layers, each built on the one below it. At the bottom sits the transistor — a tiny electrical switch that knows only 'on' or 'off'. At the top sits a program written by a programmer
A computer is a tower of layers: each layer takes simple things below it and turns them into something more powerful — from an on/off switch all the way up to a full app.
- Abstraction
- Deliberately hiding details: a layer exposes a simple interface to use and conceals the complexity beneath it.
- Abstraction Layer
- One level in the computer's tower (e.g. logic gates or machine code) built on the level below it and serving the level above it.
- Transistor
- A tiny electrical switch with no moving parts, the basic physical unit of a computer; on/off represents 1/0.
- Bit
- The smallest unit of information — a binary digit whose value is 0 or 1. The name is short for Binary Digit.
- Logic Gate
- A component built from several transistors that computes a simple logical function (such as AND or OR) over bits.
- Machine Code
- Binary instructions (sequences of 0s and 1s) the CPU executes directly; the only language the hardware truly 'understands'.
- Hardware & Software
- Hardware is the physical components (CPU, memory); software is the instructions that run on them. The boundary between them is the instruction set (ISA).
