OK, let’s start with the fundamentals. What’s inside your computer? There’s the CPU (central processing unit, often called the processor), which is the brain of the computer, performing its key functions. There’s RAM (random access memory, or just ‘memory’), which is where the computer stores what it’s doing while it’s switched on. And then there’s the hard disk, which is a more permanent store of information and files that survives when the computer is turned off.

Some computers have good CPUs, RAM and hard disks, and some don’t, so it’s important that you know what to look for. CPU speed is measured in gigahertz (Ghz), which is how many billion instructions the computer can process each second. Similarly, RAM and hard disk space are measured in megabytes (MB) and gigabytes (GB), with a megabyte being a million bytes and a gigabyte being a billion – each one representing one letter of the alphabet, or another character. This article is about 1,500 bytes long – but a single picture or mp3 song file can easily take up as much as 5 million bytes.

On top of these essentials, computers can have all sorts of additional components. One of the most popular is a graphics card, which is used for gaming and other graphically-intensive software. It is basically like an additional CPU and RAM dedicated especially to graphics, taking the weight of those heavy calculations off the main computer. Disc drives are another very useful add-on, allowing you to play CDs and DVDs, and even to write to them if you get an ‘RW’ (re-writing) drive.