Chapter intro: Units, characters and file size

Everything a computer keeps takes up room, and the machine is exact about how much. A film, a photograph, a message you typed this morning - each one has a size, and that size is measured in the same currency all the way down. This chapter, Units, characters and file size, is about that measurement: the units storage is counted in, how the letters and symbols you type get in there, and how big a piece of text turns out to be once they do.

Right, here is the whole chapter laid out on your screen, along with two quick things worth knowing before you press play on the first video.

It runs from bits and bytes and the units above them, through character sets and ASCII, the order character codes sit in, Unicode, working out the size of a text file, and finally what a fixed number of bits can and cannot hold. If you have arrived here from the chapter Binary and number bases, this is the step straight after it: that one got numbers into binary, and this one is about how much room that takes, and how everything else you type joins them in there. It is for anyone taking GCSE Computer Science on AQA, Edexcel or OCR, and where those boards genuinely differ, the videos say so.

One practical thing first: every video here carries its own short, searchable code, sitting right beside its title on the list. Take the first teaching video, Bits, bytes and the units of storage: search for ScholaFly C S oh two, oh one, and that exact video comes straight up, no scrolling needed.

Second thing: the thumbs-up under each video is really a tick-list you keep on yourself. Watch one, and if nothing in it would trip you up in a test, tap the thumb. Whatever is left without a thumb is simply what you have still got to do, so no evening gets spent on a topic you already own. If one refuses to go in, drop it into a playlist and come back to it later in the week, since a second pass is usually the one that sticks. And my commitment to you is this: if I've not done a great job teaching something and it's confusing, leave a comment, and I'll have a crack at making a better video.

Next in the chapter: Bits, bytes and the units of storage, search for ScholaFly C S oh two, oh one.

For more, visit scholafly.com, or watch the next video.