High Sierra is the name of this year’s free operating software update for Apple Mac computers. It follows last year’s release, called Sierra, and you can tell from the name that the two are related. 

It’s Apple’s way of saying that this is an evolution rather than a new start. Although that’s also what this update is, as it introduces a series of improvements to the system’s core foundation technologies, those unseen systems that power the Mac, such as the file types the computers use, of which more later.

Programs like Photos, for a start.

This is one of the best-loved Mac apps and it has been gently redesigned. Not least so the sidebar, which sometimes disappeared in previous versions, is now more visible again. Editing photos has become more sophisticated thanks to the arrival of new controls such as Curves, which allows you to make fine-tuned colour and contrast adjustments, often with transformational results.

Similarly, Selective Colour can turn a red shirt blue, for instance. There are bigger thumbnails, a wider range of topics in Memories (the video and photo compilations that the software creates automatically, complete with background music). Photos now plays nicely with third-party apps so you can edit using capabilities from Pixelmator, say, from within the Photos app. 

The Safari web browser has been enhanced with some genuinely useful updates. Intelligent Tracking Prevention means you need never be followed round in your web browsing by persistent ads: the browser uses machine learning to spot who’s tracking your browsing behaviour. This is particularly useful if you find, after you’ve taken a look at a pair of shoes, that similar ads pursue you (often after you’ve bought the product). 

And just as usefully, you’ll be able to stop websites from auto-playing video. This will be fantastic if you’re sick of music blaring out when you’re at your work computer. If you want a site to automatically play video with audio, you can make it an exception in the settings. 

There are improvements to Mail, Spotlight and a new, more realistic voice for Siri – the new voice is the same as the improved one that came with iOS 11 on iPhone and iPad.

The app I turn to increasingly for everything from secure hidden passwords to minutes for a meeting is Notes. It adds tables, better search and even pinned notes so the ones you use all the time stay above a neat grey line at the top of the page.

Universal Clipboard is a recent innovation and lets you copy a photo or text or whatever on an iPhone and then when you press Paste on another device it appears as if by magic. Now you can copy and paste between Macs, not just Macs and iOS devices.

Anyway, what about those core foundation technologies?

For around 20 years, Apple has used a file system called HFS+ as the Mac’s default file system. It was designed at a time when all computers used spinning hard drives with capacities that are now considered small. 

After all, an iPhone can now have storage of 256GB, in a non-spinning Flash drive, to boot. All that storage in something small enough to hold in your hand. It’s a different world from the one HFS+ was created for, and the system needed to be updated to a system that will work better now and into the future. 

Chances are you won’t have come across HFS+, however intensively you use a Mac. Unless you’ve reformatted your hard drive, say, where you may have seen it under its other name, Mac OS Extended.

The new default is Apple File System, APFS, and you might not come across this new system very often either. If you do, what exactly are you doing?

Anyway, APFS is a 64bit system, so it has plenty of capacity to grow as things change – above all, APFS is all about future-proofing.

It’s very flexible. The same file system is already to be found on iPhones and iPads, as it’s been part of the iOS software since version 10.3 was released in March this year. 

Unicode, the computing industry standard for consistent encoding, representation, and handling of text is key to naming files, for instance. HFS+ could only cope with version 3.2, which was highly English-focused and has become outdated. 

APFS currently supports Unicode version 9, which is more global, understanding all languages, and includes over 136,000 characters and even emoji – so you’ll be able to pictorially title your document ‘Panda Pig Poo’, if you like. Though I’m not sure it’s a title that suggests a good read.

There are more features possible with APFS, such as instant copying. Previously, when you duplicated a big video file, say, it could take a long time to finish. Now, it’s instant because the software basically just copies the metadata at first and only copies the content itself, in the background, when you actually start to edit the duplicate.

Actually, that’s emblematic of High Sierra: a faster, more efficient upgrade that does things in a new way. And it’s designed to be able to do it all with increasing efficiency, for years to come.