Main Components
A computer is made of several main components that work together. The Central Processing Unit (CPU) is the brain of the computer that carries out instructions. The CPU has two important parts: the Arithmetic and Logic Unit (ALU), which performs calculations and logical comparisons, and the Control Unit, which controls and coordinates the operation of the other components.
Memory stores data and instructions. RAM (random access memory) is volatile memory that holds data temporarily while the computer runs, and its contents are lost when the power is turned off. ROM (read only memory) is non-volatile memory whose contents remain even without power, usually holding start-up instructions.
Key idea
The CPU processes data using the fetch–decode–execute cycle: an instruction is fetched from memory, decoded so it can be understood, then executed.
Input, Output and Storage
Input devices such as the keyboard, mouse and scanner put data into the computer. Output devices such as the monitor, printer and speakers display or produce results. Secondary storage such as the hard disk and flash drive keeps data permanently for future use.
Example
When you type a letter on the keyboard (input), the CPU processes it with the help of RAM, and the letter appears on the monitor (output). When you save a file, it is copied to the hard disk (secondary storage).
Binary Representation
A computer only understands two states, 0 and 1. This system is called binary. Each binary digit is called a bit, and eight bits make one byte. All data — numbers, letters, images and sound — is ultimately represented as combinations of 0s and 1s inside the computer.
Remember
RAM is volatile (lost without power) while ROM and secondary storage are non-volatile (kept). The CPU processes, memory stores, and data is held in binary.