In a computer, information is stored as bits and bytes, at the smallest scale. A bit is too small to be of much use. 8 bits grouped together make one Byte.
A Byte therefore, is one of the two smallest units of measurement used to measure data.
A Kilobyte is a unit of measure for digital storage or data, which is equal to 1024 Bytes.
Some decades ago, a Kilobyte used to the most popular unit of measurement for data, but since the volume of information has increased significantly, it has been replaced by Gigabyte as the most popular one.
A Megabyte (MB) is a unit of data measure equal to 1024 KBs or 1,048,576 Bytes.
The most popular unit of measure – particularly in the web hosting industry – these days, the Gigabyte (GB) is equal to 1024 MBs or 1,048,576 KB.
A Terabyte is a unit of data measure which is equal to 1024 GBs or 1,048,576 MBs.
To a hard disk manufacturer, one KB is 1000 bytes, one MB is 1000 KB, and one GB is 1000 MB.
Which is technically an accurate definition given the prefixes; Kilo meaning 1,000, etc.
Given that definition, if a hard disk is advertised as 1TB, it contains 1 * 1000 * 1000 * 1000 * 1000 = 1,000,000,000,000 bytes of space. The hard disk manufacturer therefore, advertises it as a 1TB hard drive.
When actually, the 1 TB hard drive would be able to store only 931 GB or 0.909 TB of actual data.
Manufacturers of RAM however, do not manufacture their products in even groups of 1,000. When you’re buying memory, a KB is 1024 bytes, an MB is 1024 KB, and a GB is 1024 MB.