Hardware components and their roles

Hello students, welcome to Kwickprep. When you open a laptop, you see a board full of chips and tiny wires. What does each part actually do? Today we will learn the main hardware components of a computer and the role each one plays.

First, a definition. Hardware means the physical parts of a computer that you can touch. Input devices, like a keyboard or a microphone, send data into the computer. The CPU, the central processing unit, processes that data. Memory and storage hold the data and the programs. Output devices, like a screen or a speaker, show the results.

Most computers follow one important idea. Programs, which are sets of instructions, are stored in main memory together with the data. Both are held in the same memory as binary numbers. The CPU fetches the instructions from memory and carries them out one by one. This design is called the von Neumann architecture, after the scientist John von Neumann.

The CPU has four main parts. The control unit, or CU, directs everything: it decodes instructions and sends control signals to other parts. The arithmetic logic unit, or ALU, does calculations like adding, and logic like comparing two values. Registers are very small and very fast storage areas inside the CPU. The clock sends out regular electrical pulses that keep every operation in step.

Let us look closer at registers and the clock. The program counter holds the memory address of the next instruction to fetch. The accumulator holds the result of the latest calculation done by the ALU. Clock speed is measured in hertz, and today in gigahertz. A three gigahertz clock gives about three billion pulses every second.

Main memory is memory the CPU can read directly. RAM, random access memory, holds the programs and data in use right now. It is volatile, which means its contents are lost when power is switched off. ROM, read only memory, is non-volatile, so it keeps its contents without power. It stores the start-up instructions that run when you switch the computer on.

A bus is a set of parallel wires that carries signals between the CPU and memory. The address bus carries the address of the memory location the CPU wants, and it goes one way only, from the CPU. The data bus carries the actual data and instructions, in both directions. The control bus carries control signals, such as read or write, and the clock pulses.

All these parts work together in the fetch, decode, execute cycle. In fetch, the address in the program counter goes along the address bus, and the instruction returns on the data bus into the CPU. In decode, the control unit works out what the instruction means. In execute, the instruction is carried out, perhaps by the ALU. Then the cycle repeats for the next instruction, billions of times a second.

Main memory is small and RAM forgets everything at power off, so we need secondary storage. Secondary storage is non-volatile and keeps files for a long time. Magnetic storage, like a hard disk drive, stores data on spinning magnetised disks. Solid state storage, like an SSD or a pen drive, uses flash memory chips with no moving parts. Optical storage, like a DVD, uses a laser to read tiny marks on a disc.

Finally, the devices around the computer. Input devices, like a keyboard, a mouse, a microphone or a scanner, bring data in. Output devices, like a monitor, a printer or a speaker, present results to the user. A touchscreen on your phone is both an input and an output device. Sensors, like a temperature sensor, send real world data into a computer system.

Hardware is not only inside laptops. An embedded system is a small computer built into a larger device. It does one dedicated job, again and again. A washing machine controller, a microwave oven and the anti-lock brakes in a car are all embedded systems.

Pause and predict. You are typing a school project and have not saved it. Suddenly, the power goes off. Was the unsaved work held in RAM or in ROM? It was in RAM, which is volatile, so the unsaved work is lost, while saved files on the SSD are safe.

Let us revise what we learned today. The CPU contains the control unit, the ALU, registers and the clock. RAM is volatile and holds running programs, while ROM keeps the start-up instructions. The address, data and control buses link the CPU and memory. Secondary storage can be magnetic, solid state or optical. Input and output devices connect the computer to the user.