Rather than buying a separate PC, keyboard and display, all-in-one PCs offer convenience and style. Here's our guide to choosing an all-in-one PC.

The all-in-one PC is now the most popular type of personal computer in the world. For most people, it takes the form of a portable battery-powered device with a fold-down screen – otherwise known as a laptop. For more static installations, the all-in-one (AIO) desktop PC offers a much larger screen with a separate keyboard and mouse.

Most current AIO designs are based on the design of the flatscreen Apple iMac. Screen sizes span from around 21in to 27in, and all the PC electronics are housed in the same frame, behind and below the dominant LCD panel.

Because internal space is more limited, and therefore cooling systems too, AIO PCs tend to have lower power components than traditional PC boxes. Expect to see mobile versions of Intel processors, for example, which are optimised for reduced heat output.

Similarly, graphics capability will be reduced somewhat, often with laptop-spec graphics processors; or frequently in the case of Windows AIO PCs, with no dedicated graphics at all. The integrated graphics used instead are capable of playing high-definition video, but you will be limited to which computer games you can play.

Like a laptop, an AIO PC is a one-stop solution, and requires most of its features to be incorporated at the time of manufacture. You cannot, as you would with an enthusiast’s gaming PC, upgrade the graphics card later, for example.

See also: Group test: what's the best all-in-one PC?

Expect to see all the features you’d find on a decent laptop: 802.11 Wi-Fi, Bluetooth, webcam, built-in microphone and stereo speakers.

Windows AIO PCs are often promoted with touchscreen displays, although it might not be until Windows 8 is released that we will discover how worthwhile this will be. If you do select an AIO with touchscreen display, check screen image quality as this has traditionally been compromised by adding in the technology. Similarly, a trial of the screen’s sensitivity is recommended, as this will often be poorer in recognising finger touches compared to the best smartphone and tablet touchscreens.

As we advise with any monitors, ensure image quality, contrast ratio and colour gamut are up to scratch – the screen is where you’ll be focused whenever you use the PC. And when the display is integrated into the PC, it’s impossible to replace a poor screen choice later without finding a complete new AIO.

Some AIO designs allow you connect a second display, to extend the desktop or even connect to a large TV or projector. Similarly, some design include an HDMI video input, letting you connect a games console or BD player and display their output on the AIO’s screen.

Blu-ray is a common feature, but check if the drive will write to blank BD discs or just read commercial Blu-ray films.

Some AIO PCs incorporate digital TV tuners. Even if not included, these are simply added later as a USB dongle.

As a computer that you sit much closer to, acoustic design and ergonomics are even more important than with a tower that sits on the floor. Check how noisy the PC is – too many PC makers do not understand that their products will be used by humans who do not wish to spend time next to whining and rattling machinery. With no concession to quiet operation they will be distractingly noisy.

Speakers are often built-in. Don’t expect full-range fidelity, but you should be able to enjoy clear enough sound to watch films and play music. For better sound, look for line-level audio output to connect to an external sound system; or better yet an S/PDIF digital output for a hi-gi system.

The right number and right type of ports are crucial on an AIO. As with screen choice, there’s no opportunity to change or add more later.

For Windows PCs, expect to see USB 3.0 as well as legacy USB 2.0. For Apple Macs, USB 2.0 ports are joined by FireWire 800 and now, Thunderbolt, which provides the fastest desktop computer interface of them all.

Remember peripherals supplied with the PC. Wireless keyboards and mice give a cleaner desktop but will require periodic battery replacement. Bluetooth peripherals will not require a separate USB dongle that takes up a USB port. Most mice give basic left-right click control, while more sophisticated multi-touch mice such as the Magic Mouse supplied with the iMac give plenty more useful ways to interact with pages and images on-screen.