The history of modern computing is a constant struggle between decentralisers and recentralisers. In the 1980s the shift from mainframes to personal computers gave more power to individual users. Then Microsoft clawed back some of that power around its proprietary operating system. More recently, open-source software, which users can download for nothing and adapt to their needs, took over from proprietary programs in parts of the industry—only to be reappropriated by giant technology firms to run their mobile operating systems (as Google does with Android) or cloud-computing data centres (including those operated by Amazon, Microsoft and Google).