Our Computing Galaxy

Painting a picture splits into thousands of tiny jobs, so the GPU's big team wins. But a puzzle where every step needs the step before can't be shared, so the CPU's fast, clever cores win that one.

This is why computers have both. GPU cores are simpler and a bit slower one by one, but there are hundreds or thousands of them (parallel processing). CPU cores are fast and flexible for tasks that must happen in order. AI and graphics are "embarrassingly parallel": perfect for GPUs.

RAM is your desk: fast, but cleared when the power goes off. The SSD is the library: it keeps everything until you delete it.

RAM is "volatile": it needs power to hold data. When the desk overflows, the operating system parks things on the SSD (called swap), which is much slower. That's why more RAM makes a computer feel faster with many apps open.

Each switch is worth double the one to its right: 1, 2, 4, 8, 16, 32, 64, 128. Add up the switches that are on to get the number. Computers agreed that 65 means "A".

This letter code is ASCII (today extended by Unicode, which covers emoji and every alphabet). Photos are bytes for each pixel's red, green and blue; music is bytes for sound waves. Our 16GB of RAM holds about 16 billion bytes.

Logic gates are tiny decision makers built from transistors. Join enough of them together and they can add numbers, remember things and run games.

An XOR plus an AND make a "half adder" that adds two bits. Chain adders and you can add big numbers. A modern CPU is billions of transistors forming gates like these, switching billions of times per second.

Always read a web address from the right. The ending (.com, .net, .gov) comes first, then the real name just before it. That real name tells you who owns the site.

The ending is the top-level domain (TLD). The name before it is registered by its owner. Anything further left is a subdomain the owner creates, so only minecraft.net's owner can make games.minecraft.net. Tricksters put famous names on the left of their own domain to fool people.

Length beats tricks. Four or more random words are long, easy to remember and very hard to guess. Never share passwords, except with your grown-up.

Every extra character multiplies the number of guesses. This lab assumes a robot guessing 10 billion times per second. Real attackers try common words first, so pick truly random words, and turn on two-step login (MFA) so a stolen password alone is not enough.

Julius Caesar shifted letters to hide messages. Only someone with the key can read them. The lock icon in your browser means your messages are scrambled the same way, but much more cleverly.

A Caesar cipher has only 25 keys, so a computer cracks it instantly (try the button). HTTPS uses encryption with keys so huge that even every computer on Earth working together could not try them all. Quantum computers may one day break some of today's methods, which is why new "post-quantum" encryption exists.

Entangled qubits are partners. Measure one, and you instantly know the other will match, every single time. Separate qubits only match about half the time, by luck.

Superposition lets a group of qubits explore many possibilities together, and clever algorithms use interference to boost the right answer. The coin picture is only an analogy: real qubits follow quantum maths, and measuring always gives a plain 0 or 1.