Block diagram of a computer
In the above diagram, Input Unit consists of devices used to transmit data to the computer's Main Memory (RAM) where they are available for processing. The Processor Unit (CPU) which is known as the brain of the computer consists of two major components that are arithmetic logic unit (ALU) and control unit (CU). Arithmetic Logic Unit (ALU) performs all arithmetical (+, -, *, /) and some logical ( <, >, <=, >=, <> ) operations and Control Unit (CU) controls the entire operation of the computer. It also controls all devices such as memory, input/output devices connected to the CPU. Output Unit display/print output on screen/paper after processing of data. If we want to store output information permanently then we need to use some other type of storage technology known as secondary or auxiliary storage.