Hardware and software

Pick up your phone. You are holding about a hundred grams of glass, metal and plastic, and not one gram of it knows what a message is. Everything you use it for is a set of instructions. They weigh nothing, you could never hold one, and without the hundred grams they would run nowhere.

That is two things in one hand, then: the hundred grams, and the instructions running on it. A question can ask you to define either one, and hardware goes first, because it is the one you could drop on your foot. Here is that first sentence, then, and on its own it is a complete answer. Hardware is the physical parts of a computer system. The parts that physically exist, that you could pick up. And the version that comes back instead, which earns nothing: hardware is a keyboard, a mouse and a monitor. Three real devices, and no mark. What is missing from that answer? It never says what kind of thing hardware is. A definition says what kind of thing something is; an example only points at one of them. And there is good news in the reports on this one. An examiner's report puts it like this: "A high proportion of responses gave good definitions of hardware." If you can already say it, you are with most of the students who sat that paper. That is where the mark goes. An examiner's report puts the same split plainly: the definition of hardware was better answered with students being able to gain 1 mark for the question. However, some students provided examples of hardware rather than a definition. And examples are still useful, remember. They just cannot do the job of that sentence, and they only make sense once the sentence exists. So the fix is an order. Write the sentence first, then put the examples underneath it, and never the other way round.

Software next, and it takes the same shape as that hardware sentence. One sentence, saying what kind of thing it is. Here is the second of the two. Software is the programs and the data that run on the hardware. The instructions that tell the hardware what to do. And the version that comes back instead is short, and it is perfectly true: software is the stuff you cannot touch. That sentence is true. Why does it still score nothing? It only says what software is not. The mark is for what it is, and a negative never reaches it. An examiner's report lists it as a common wrong answer: common incorrect answers when defining software included either stating that was non-physical. Lead with what it is, then. The programs and the data that tell the hardware what to do. Then, if you want, add that you cannot hold it.

That leaves a third thing to say about those two sentences, and it is the one that gets left out. How hardware and software need each other. Now picture a brand new laptop, lifted out of its box, with nothing installed on it at all. You press the power button and the light comes on. The light is on. What can that laptop actually do? Almost nothing. It is a case full of working parts with no instructions telling them what to do. And that is the relationship, in one line, with that empty laptop saying it. Hardware with no software does nothing at all, and software with no hardware has nowhere to run. So carry the count: two words, two sentences, two marks. Hardware is the physical parts, and software is the instructions that run on them. Plenty of students write one sentence and stop there. An examiner's report on a question asking for both definitions records this: less than half of the students were able to gain both marks. So two words in the question means two sentences in the answer. Write one, write the other, then add the line about how they need each other.

Now six things to sort, hardware or software, and one of them is harder than the other five. A graphics card, a web browser, a printer, a spreadsheet file, a hard disk drive, and the code that runs a lift in a block of flats. And the rule is the one you already have, from those two sentences: a physical part, or instructions and data. Can you sort all six, and name the one that was hardest to place? The graphics card, the printer and the hard disk drive are hardware. You could pick all three of them up. The web browser is software, and so is the spreadsheet file, because software is the programs and the data they work on. The hard one is the last: code running on machinery nobody would call a computer, and it is software all the same. Machines built like that get a video to themselves at the end of this chapter, called Embedded systems.

Two sentences were the whole job here. The questions come first, and the answers land afterwards. What is hardware, in one sentence with no example inside it? Hardware is the physical parts of a computer system. The parts that physically exist and that you could pick up. Now software. What is it, in a sentence that does not start with not? Software is the programs and the data that run on the hardware. The instructions that tell the hardware what to do. One more, and this one is new. A saved photo on your phone: hardware or software? Software. A photo is a file, and files count every bit as much as the code that opens them.

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Next in this chapter: The CPU and the von Neumann model, which opens the box you have just defined.

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