OS showdown: Windows 10 vs Windows 8.1 vs Windows 7

OS showdown: Windows 10 vs Windows 8.1 vs Windows 7

What's really new in the latest version of Windows

It's easy to think that the main difference between Windows 7, Windows 8 and 8.1 and Windows 10 is the interface; whether you have a Start menu or a Start screen, whether you use desktop programs or apps from the Windows Store. But the fundamental changes in security, performance and mobility are just as important. As Windows develops, you gain and lose features, but the underlying operating system platform changes are more significant, if not always as obvious.

Windows 7: Faster, smaller, better

When it came out in 2008, Windows 7 had new user interface features – a taskbar you could pin icons to, jump lists, aero snap – and plenty of security improvements. But the changes under the hood were also significant.

Windows 7 began the process of making the Windows code base smaller, reversing the trend where new versions of Windows had needed larger and more powerful PCs to run on. That was partly an understanding that Moore's Law was under pressure (as ever-smaller nanometre production processes were going to hit the limit of silicon so small you can't reliably fit in enough electrons – meaning that chips weren't going to keep up the same pace of getting faster and more powerful every year), and partly a response to the popularity of netbooks and the rising interest in mobile.

That also meant making features like wireless networking, Bluetooth connections, mobile broadband and hibernation more reliable, and there was even support for touchscreens (as well as pens, for tablet PCs), and accelerometers.

But Windows 7 was also the first time Microsoft was able to take advantage of an internal refactoring it had been working on for five years, trying to untangle the interlocking spaghetti of code that makes up the operating system. Called MinWin, this let the team building Windows improve specific pieces of their code without worrying about how they depended on other code, so it was easier to update and add new features.

Windows 7 improved battery life by adding power management to the BIOS and even to hardware drivers, so the system could turn off unused devices – like the USB port if nothing was plugged in – and power down parts of the CPU to reduce so-called idle power (how much energy it takes to run a PC when you aren't using it to do anything). This was also when Windows began to stop applications interrupting the CPU, so that it could spend more time in a low-power state between instructions (a setting Chrome continues to change, prioritising performance over power savings).

Windows 8.1: More than just Metro

The full-screen Start screen, the charm bar and the new smartphone-style apps (known at the time as Metro) that opened in their own windows were the most obvious new features of Windows 8 (and the Metro-only Windows RT version that ran on ARM tablets), and the emphasis on touch alienated plenty of desktop and mouse users.

But Windows 8 was also crammed with support for new hardware, significant security improvements like secure boot, improved biometrics and a new firewall with packet filtering, a Windows To Go option for running Windows straight from a USB stick, improvements to Direct X, and a version of Hyper-V for virtualisation that was almost exactly the same as in Server 2012.

It added connected standby – a way of powering down PCs with SoC CPUs so that they could stay connected, so email would be up to date. Windows 8 also improved battery life by measuring the power usage of every single component in a PC and then turning them on or off in the most efficient order.

A year later, Windows 8.1 put the Start button back, let you choose to boot straight to the desktop and made some changes to the Metro interface to let you choose what size window each app appeared in. But it also added a wide range of security and management improvements for business users and built in support for more new hardware, from Miracast for streaming your screen to another device to Wi-Fi direct printing.

It also integrated OneDrive (then called SkyDrive) with Explorer. That meant signing in with your Microsoft account didn't just get you apps from the Store and sync your settings to other PCs; it let you see and save files in the cloud, even if you weren't connected.

Windows 10: Forward and back

With Windows 10, Microsoft has backed off on many of the ideas of Windows 8. Metro apps – now known as Universal apps – run on the desktop like any other app, but the same app can run on a PC, a Windows 10 phone, Xbox One and even HoloLens. OneDrive integration is far more basic – you can still choose what folders to sync but you no longer see the list of your folders when you're not online. The charm bar is gone, replaced by an iOS-style Action Center for notifications.

There's a brand new browser called Edge, that's far more like Chrome, while Internet Explorer is only there for compatibility with older business sites (although IE will likely get a lot of use until Edge gets more of its missing features later this year).

Again, there are plenty of security improvements, from the Windows Hello system that can log you in with your face or iris as well as your fingerprint, through to two-factor authentication, containers to protect business data, and more ways of using Hyper-V to protect your information. The performance improvements continue, and the new way of installing the OS is faster and more likely to be able to keep your files and software. Windows 10 is even better at cleaning up after installs and updates so it leaves more disk space free.

Away from the user interface changes, which are designed to make Windows 10 work well with the mouse and keyboard while still being fairly easy to use on a tablet, many of the improvements build on the developments in Windows 7 and Windows 8.1. And the shift to Windows as a Service, where you keep getting new features without getting a new version of Windows, means that these major updates from one release of Windows to the next, might become a thing of the past.

Microsoft is hoping that instead of deciding whether to shell out for an upgrade to the next version of Windows based on specific new features, that you'll just keep using a PC with Windows and get the features as they come along.