computer storage devices and memory units

Area where we store Data or Information is called as computer data storage, in other way we can call it as storage or memory, this is a main functionality of computer. All type of manipulations and computations performed in the central processing unit (CPU) of a computer. As per the Von Neumann architecture, the CPU is made up of two main parts: control unit(CU) and arithmetic logic unit (ALU). The control unit controls the flow of data between the CPU and memory, while ALU performing any arithmetic or logical operations on data. The most common unit of storage is the byte, and 1 byte is equal to 8 bits. 1 bit is nothing but alphabet, numbers, pictures pixel, audio, video, or any other form of data or information can be converted into a string of bit, or binary number form, which is a value of 1 or 0. Below table will specify the units of memory storage.

Sr. No.	Unit	Description
1	1 Bit	A binary digits as 0 & 1
2	1 Nibble	A group of 4 bits
3	1 Byte	A group of 8 bits, and 2 nibbles
4	1 Word	It is group of byte, which varies from computer to computer, but is fixed for each computer
5	1 Kilobyte (KB)	1024 bytes
6	1 Megabyte (MB)	1024 KB
7	1 Gigabyte (GB)	1024 MB
8	1 Terabyte (TB)	1024 GB
9	1 Petabyte (PB)	1024 TB

Memory storage types:

Memory storage is again divided in three sections, which are primary storage, secondary storage and Tertiary storage.

I]Primary storage: CPU has direct access to Primary storage or it is referred simply as main memory or internal memory. As CPU is directly connected with main memory by memory bus so CPU continuously read the instruction from the memory and stored data to the main memory. This is volatile storage means it lose the data when there is power supply interrupt at any time. i.e. RAM(Random Access Memory)    

II]Secondary storage: Secondary storage is known as external memory or auxiliary storage, which is differs in functionality from primary storage as it is not directly accessible by the CPU. There is not direct connection from CPU. The computer usually uses its input/output channels to access secondary storage. Secondary storage does not lose the data when there is power supply interrupt at any time, so it is known as non-volatile storage. i.e. ROM(Read Only Memory), CD or DVD