How can a photo, a song, and a text all travel down the same wire?
Short pages, a few minutes each. Enrolled in our Runestone course? Open them from there so your progress counts.
Step 1 of the photo trip. Before anything can be sent, it has to become bits — and it turns out everything becomes the same kind of bits.
A wire can do two things: carry a signal, or not. On or off. That is the entire vocabulary a computer has to work with, and it never gets richer than that.
So the trick computers use is this: agree on what patterns mean. If everyone agrees that 01001000 means the letter H, then H can travel down a wire that only knows on and off.
The remarkable part is not that text works this way. It is that everything does. A photo is a grid of colors, and each color is a number. A song is the height of a sound wave measured thousands of times a second, and each measurement is a number. Numbers are bits.
That is why one wire can carry all of it. To the wire, there is no difference between your music and your homework.
Grid paper, 8×8. Draw something simple in black and white — a letter, a smiley, an arrow. Fill squares in completely or leave them blank.
Now write it as bits: 1 for filled, 0 for blank, reading left to right, top to bottom. You will end up with 64 digits.
Hand only the digits to a partner — not the picture. Can they rebuild it?
If they can, you just did what your phone's camera does, by hand, at a rate of about one pixel per second instead of twelve million.
Do it on paper first — that is the part that sticks. Then use this to check your work, or to trade with someone across the room.
Click squares to fill them. 1 is filled, 0 is blank, read left to right and top to bottom — the same order you used on paper.
You only need to recognize these today. Every one gets taught properly later.
Hold onto that second question. Unit 1 answers it, and the answer is genuinely clever.