Computer Memory is made up of semiconductor material, typically Metal Oxide Semiconductor(MOS) organized as a cell.
Register memory is a very small piece of very high speed memory. Data for Arithmetic operations are loaded into registers. Once Arithmetic operations are done, it will be stored in the RAM
RAM is volatile or temporary memory. Volatile memory loses the data when the electircal power is OFF.
- RAM stores data and input that user provides temporarily before and after it is processed by CPU. Data moves between RAM and registers.
- Once the processing is done, the data is either stored in the secondary storage or discarded. Data moves between RAM and secondary storage.
ROM is read-only and non-volatile memory. ROM stores the firmware required to start the computer.
Cache is volatile memory placed closed to CPU. Cache speed is faster than RAM and less than Registers. Hence, CPU uses cache to temporarily store data needed to be moved frequently to and from regiters.
Internal hard disk drive
Internal hard disk drive (HDD) non-volatile permanent internal storage that is inside the Desktop or Laptop. Popular size of hard disk as of today is 1TB
External Hard Drive
External hard disk drive (HDD) non-volatile external storage that is connected to the Desktop or Laptop via USB cable. Popular size of hard disk as of today is 1TB, 2TB, 4TB,8TB or 16TB.
Solid State Drive
SSD Solid State Drive is 3 to 10 times faster to access than Hard Disk Drive. SSD is expensive compared to HDD. Laptops as of 2022 come with 1TB Hard disk drive / 256 or 512GB SSD.