Besides the microprocessor, the system unit also contains a storage area where the data is stored before being actually processed. This storage area is called the internal storage. It is also referred to as primary storage, main memory ox Random Access Memory (RAM).
Internal storage capacities may differ in different PCs. Typically; a PC will have an internal storage capacity of 640,000 characters or more.
In computer terminology, the storage capacity of a PC is measured in terms of bytes, where one byte can store one character. Character here refers to any alphabet, number or other symbol. Therefore, to store the word COMPUTER, 8 bytes would be required. Just as there is a basic unit, gram, and another unit, kilogram to measure weight, there is also byte and kilobyte (KB) to measure storage capacity. One KB is approximately equal to 1000 bytes. Therefore, 1 KB can store approximately 1000 characters. Another common unit of measurement of storage capacity is the megabyte (MB), which is equal to approximately 1000 KB. Very large storage capacities are measured in terms of gigabytes (GB). One GB is approximately equal to 1000 MB.