Abacus

An ,abacus also called a counting frame, is a calculating tool for performing arithmetic processes. Nowadays, abaci are often constructed as a wooden frame with beads sliding on wires, but originally they were beads or stones moved in grooves in sand or on tablets of wood, stone, or metal. The abacus was in use centuries before the adoption of the written modern numeral system and is still widely used by merchants and clerks in China, Japan, Africa, India and elsewhere.

Computer

It is a programmable machine.

The two main principal characteristics of a computers are:

It responds to a specific set of instructions in a well-defined manner.

• It can execute a prerecorded list of instructions .

Modern computers are electronic and digital. The actual machineries are ( wires, transistors, and circuits) called hardware; And the instructions and data are called software.

All general-purpose computers require the following hardware Components:

Memory : Enables a computer to store, at least temporarily, data and programs.

Mass Storage Device : Allows a computer to permanently retain large amounts of data. Common mass storage devices include disk drives and tape drives.

Input Device : Usually a keyboard and mouse, the input device is the conduit through which data and instructions enter a computer.

Output Device : A display screen, printer, or other device that lets you see what the computer has accomplished.

Central Processing Unit (CPU): The heart of the computer, this is the component that actually executes instructions.

In addition to these components, many others make it possible for the basic components to work together efficiently. For example, every computer requires a bus that transmits data from one part of the computer to another.

Computers can be generally classified by size and power as follows, though there is considerable overlap:

Personal Computer : A small, single-user computer based on a microprocessor. In addition to the microprocessor a personal computer has a keyboard for entering data, a monitor for displaying information, and a storage device for saving data.

Workstation : A powerful, single-user computer. A workstation is like a personal computer, but it has a more powerful microprocessor and a higher-quality monitor.

Minicomputer : A multi-user computer capable of supporting from 10 to hundreds of users simultaneously.

Mainframe : A powerful multi-user computer capable of supporting many hundreds or thousands of users simultaneously.

Supercomputer : An extremely fast computer that can perform hundreds of millions of instructions per second.