The common definition of computer is: a machine that manipulates data according to a list of instructions. The first devices developed to resemble a modern computer were first made in the mid-20th century , although similar machines had been constructed earlier. The first electronic computers were the size of a large room, consuming as much power as several hundred modern personal computers or PC. Modern computers based on tiny integrated circuits are millions to billions of times more capable than the early machines, and occupy a fraction of the space. Nowadays simple computers are small enough to fit into your mobile phone or watch , and can be powered by a very small battery. Personal computers or Desktop computers in their various forms are classic examples of the modern age. Computers are made of several critical components, known as Hardware like: Motherboards, Monitors, CPUs and Software like: Antivirus, Operative Systems and Utilities.