The clock is a mechanical, electrical or atomic device that measures the passage of time. Mechanical models date from the late Middle Ages. All mechanical models must have a sourse of energy - for example a falling weight or a wound spring. All such models must be carefully regulated to make them run accurately. The energy turns  a system of wheels that move the hands.

      The computer is based on a microprocessor, a small chip that performs the operation of a central processing unit. The early kinds of computers had a rather small memory, typicaly in the megabyte which is great improvement. Computers has changed peoples lives. We are can not imagine our lives without computers and internet of course.

      The laser is generates ,, well organized,, light. The mechanism uses a process known as stimulated emission. It generates electromagnetic radiation in a special microwave region. Nowadays these devices sre widely used in different ways, among which is medicine. The laser is often used to make quick and painless operations.