Computers, creativity and learning: What's inside a computer?

I'm working on some materials for primary school teachers to help them teach children about computers. Can you help? For the moment, I am concentrating on how a computer works, based on some interview work I did with primary kids which showed they were confused about this and would like to know more. Below are my attempts at clear and concise explanations. Turns out it's hard to write these well!

If you're a teacher, is there anything else you need to know about this topic, or anything which is not clear?
If you're a computer scientist, is there a key concept I have missed, or anything which is deeply misleading?

What’s inside a computer?

There’s an electronic chip inside every computer, laptop, tablet or phone. The chip needs electrical power to work, which is why you need to plug in your computer, or charge the batteries of your tablet. The chip contains a processor which is like the computer’s brain. It also has memory for storing information it is working on now, and a hard drive for information it will need to store for a long time. The processor has got billions of little electronic switches inside it. The switches can each be set to “off” or “on”. The computer has instructions in its memory which tell it what to do. The messages are written in binary code which means they only contain 1s and 0s. A “1” means “turn a switch on”, and a “0” means “turn a switch off”. When you type, the keyboard sends a message to the processor about which key you have pressed and the processor uses the instructions in its program to decide what to do.

For older children, the following additional information might be appropriate:

Over the years computer chips have got faster and smaller and they’re capable of following instructions to do very complicated tasks. But the basic design of the chip hasn’t changed very much since it was invented in 1945 by the American mathematician John von Neumann.

What does a computer do when it follows instructions?

Imagine you have written a program in Scratch which adds together two numbers. When you press the green flag to make your program run, how does the computer follow the instructions you have written? Scratch is designed to be easy for people to learn using words and pictures we can understand. The computer processor works with binary code but it would be very confusing for people to have to write instructions all in 1s and 0s. So programs written in Scratch or other high level languages get translated before they run on the processor. When you press the green flag to tell Scratch to run your program, the computer follows rules which eventually turn your jigsaw blocks into binary code instructions which the processor can follow by turning its switches on and off. Once it has worked out the answer to the sum you gave it, the answer is translated from binary code and passed back to Scratch to show on the screen.

For older children, the following additional information might be appropriate:

Another name for a computer programs is software. The programs which translate the instructions are called compilers or interpreters. In fact, a program might get translated several times between different computer languages before it becomes binary code. Computers nowadays usually have lots of different layers of software stacked on top of each other to make them easier to program. You can think of it like a tower of stacking cups with the computer processor at the bottom. Your Scratch program is on the top cup, and it gets translated into a language called Action Script in the next level down in the stack. Action Script runs within a web browser program like Chrome. In turn, instructions from Chrome get translated to C++, which is then turned into assembly code and then finally binary code to run on the processor.

[INSERT IMAGE OF ANNOTATED STACKING CUPS HERE]

2 Comments

It is really tricky to do this well. I think most of what you have written is great.

The main thing that strikes me as not quite right is saying that the processor is like a brain. Partly because a human brain has memory too, so that could get confusing. Also because I'm not sure whether saying it is like a brain helps get to the point of what a processor does. It acts on items in memory according to the given instructions.

Perhaps it is more like a worker in a warehouse, picking up items and moving them to new locations, unpacking and combining them according to the instructions it is given. That metaphor has its own limitations and may not be suitable for this audience. There might be something better and simpler but that is all that I can come up with right now!

Posted by: Tim | September 26, 2016 at 04:52 PM