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F01

What Is a Computer?

“A computer is a giant room of light switches”

Lessons

Start the course →0 of 14 lessons done
  1. A room full of light switchesFreeEvery computer is built from tiny on/off switches called bits. Each extra switch doubles what you can say. · 8 min
  2. Counting with switchesFreeBinary numbers give each switch a value (1, 2, 4, 8…). Add up the switches that are on to get the number. · 10 min
  3. Turning letters into numbersFreeText is stored by giving every character a number (A = 65), then storing that number in binary. That shared list is called Unicode. · 9 min
  4. Hexadecimal and byte sizes🔒 MembersLong rows of 0s and 1s are hard to read, so programmers write each group of 4 bits as one hexadecimal digit (0–9, then A–F). And bytes add up into KB, MB and GB. · 10 min
  5. Pictures as numbers🔒 MembersA digital picture is a grid of tiny colored squares called pixels. Each pixel's color is three numbers, how much red, green and blue light to mix. · 10 min
  6. Sound and video as numbers🔒 MembersSound is a wave. Computers measure its height thousands of times a second and store each measurement as a number. Video is a fast flipbook of pictures plus sound. · 10 min
  7. Logic gates🔒 MembersA logic gate is a tiny circuit that looks at on/off inputs and produces an on/off output by a simple rule (AND, OR, NOT). Every computer is built from billions of them. · 12 min
  8. Adding with gates🔒 MembersChain a few logic gates together and you get a circuit that adds binary numbers. This is how a computer does math, with no "math" part at all, just gates. · 12 min
  9. How a computer remembers🔒 MembersA loop of gates can hold one bit steady. Millions of those, arranged in numbered slots called addresses, make the computer's memory (RAM). · 11 min
  10. The CPU: fetch, decode, execute🔒 MembersA program is a list of simple instructions stored in memory as numbers. The CPU repeats one cycle forever. Fetch the next instruction, work out what it means, do it. · 14 min
  11. From your code to the chip🔒 MembersComputers are built in layers, each hiding the messy details of the one below. Compilers and interpreters translate your code down the layers; the operating system shares the hardware between programs. · 12 min
  12. The speed ladder🔒 MembersFast memory is small and expensive; big storage is slow and cheap. Computers stack them in a hierarchy and keep the data you'll need next close to the CPU, in caches. · 10 min
  13. How computers talk🔒 MembersThe internet chops messages into small numbered packets that travel independently through routers and get reassembled. IP addresses say where, DNS turns names into addresses, and protocols are the agreed rules. · 12 min
  14. Boss level: the mystery file🔒 MembersUse everything from this course (bits, hex, text encoding, pixels and file sizes) to figure out what an unknown file contains. · 20 min

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Placement tests are coming soon. Until then, you can mark it as known so it’s colored in on your map. You can undo this any time.