Q.Explain the different functional units of a computer with the help of a block diagram, describing how data flows through them.

A computer is organised into a few units that together carry out input, processing, storage, and output; the answer should name each unit, its role, and how data moves between them.

These units together perform the information processing cycle of input, processing, storage, and output.

A computer is organised into a small set of functional units that together carry out the four basic operations — input, processing, storage, and output. These units, shown in the block diagram of a computer, are as follows (Section a).

The block diagram places the input unit on the left, the CPU in the centre (containing the control unit and the arithmetic & logic unit), the memory unit alongside the CPU, and the output unit on the right. Solid data-flow paths run Input -> Memory -> CPU -> Memory -> Output, while the control unit sends control signals to every other unit.

1. Input unit. This unit takes in data and instructions from the user through input devices such as the keyboard, mouse, and scanner, and converts them into the electronic form the computer can understand. It is the computer's way of receiving information.

2. Central Processing Unit (CPU). The CPU is the brain of the computer, where the actual processing happens. It has three parts:

• The arithmetic and logic unit (ALU), which performs all arithmetic (add, subtract, multiply, divide) and logical (comparison) operations.
• The control unit (CU), which fetches instructions from memory, decodes them, and sends control signals to every other unit so that the work is carried out in the right order.
• Registers, the tiny, very fast stores inside the CPU that hold the data and instructions currently being processed.

3. Memory unit. This unit stores data, instructions, and results. It has primary (main) memory (RAM and ROM), which works directly with the CPU, and secondary storage (hard disk, pen drive), which keeps data permanently.

4. Output unit. This unit gives out the finished results to the user through output devices such as the monitor and printer, converting the computer's electronic signals into a form the user can see or hold.

How data flows. When the computer runs, data and instructions enter through the input unit and are placed in the memory unit. The CPU fetches them from memory, the ALU processes them, and the results are sent back to memory. From memory, the finished results move to the output unit and are given out to the user. Throughout this process, the control unit continuously sends control signals to every other unit, keeping the input, processing, storage, and output steps working in step with one another. This complete sequence is the information processing cycle: input -> processing -> storage -> output.

Do not forget the memory unit or the control unit's coordinating role — many students describe only input, CPU, and output. Also remember that the ALU and control unit are inside the CPU, not separate units alongside it.