The memory is measured by the following units:

(a) BIT (Binary digit)
It is the smallest possible unit of information. It can be either 0 or 1.
(b) NIBBLE
Four bits form one nibble

 (c) BYTE
It is a unit of information consisting of fixed number of bits. It is a combination of 8 bits
(d) CHARACTER
It is represented by one byte. It can be a letter, digit, punctuation mark or special characters.
(e) WORD
The combination of 2 bytes or 4 bytes or 8 bytes is a word.
The data measurement is as follows:
8 bits - 1 byte
1024 bytes - 1 kilobyte (KB)
1024 KB - 1 Mega Byte (MB)
1024 MB - 1 Giga Byte (GB)
1024 GB - 1 Tetra Byte (TB)
(f) SECONDARY STORAGE (Backing/Auxiliary Storage):
(a) Magnetic disk - it includes the following:
Hard disk – Rigid, Floppy disk - Flexible
(b) Magnetic tape
(c) Magnetic drum
(d) Mass storage Device - cartridge
(e) Optical Disks - CD ROM (Compact Disk - ROM)