How Computers work ?

CPU-RAM-HDD

CPU

Computer systems have a CPU (Central Processing Unit) at their core. This performs all the calculations, operations and tasks that need to be done while somebody uses the computer. The speed of the CPU is normally measured in Gigahertz. Companies that make CPU's include intel and AMD. In general, the higher the speed, the faster the computer system will run.

RAM

Another measure that affects computer performance is the amount of RAM (Random Access Memory). This stores data that is currently in use- the more memory you have the more data and programs you can have open at one time. A modern desktop PC will probably have about 1-8 Gigabytes of RAM. Memory that loses its data when the power is removed is known as volatile memory.

HDD

For perminant storage of data, most computers still have a hard disk drive or HDD. These work by magnetically storing binary code onto a metal disc. A modern computer will probably have a HDD that can store between 500MB and 1TB of data. There is 1024 Gigabytes in 1 Terabyte.
Inside your computer - Bettina Bair