A recent development in the desktop PC world has been a modest diversification of the system case. The typical business PC comes in a mini-tower box, which is probably best sited under or next to your desk.
But if space is at a premium, a smaller case would be a better choice. Dell, for example, delivers its Optiplex models in mini tower, 'thin' desktop and 'compact' small form factor sizes, each model occupying offering the same computing power but in a different case.
Three other formats that have grown in popularity are
 All-in-one, otherwise known as AIO, which combine the monitor with the base unit. The move to power-efficient components, the falling price of LCD panels and the ubiquity of touch functionality make AIO an increasingly popular choice in businesses. The all-in-one PC essentially resembles a slightly larger than normal LCD display that contains the processor, hard drive and memory built-in to the screen casing. The end result is a very elegant, clutter-free desktop PC.
 Ultra-small form factors, otherwise known as net tops or mini PCs, which borrow a lot of their designs (and components) from laptops. They are essentially laptops without a screen, input peripherals and a battery.
 HDMI dongles which have been inspired by tablets and smartphones and often share parts with the latter. These are usually used for display signage or and in niche markets. They are usually not powerful enough for most tasks but things are likely to improve by the end of 2016.