The system installed on it is Mac OS High Sierra and this replaces a very old MacBook (2008) with Mountain Lion installed on it which was starting to lose connectivity to websites - clock needs resetting (which it didn't - I suspect the problem was that the system was too old and therefore was not supported by Apple, Google, my bank and various others). I really appreciate the quality of MacBooks and their durability in this age we live in, when so much of what we buy are throwaway products in 2-3 years (even at the prices charged for those products).