1.7 - Units of Measurement
Exam Board:
OCR
Specification:
2016 - Unit 1
All computer systems communicate, process and store data using binary because this is the format that the processor understands.
Binary is a number system consisting entirely of 0s and 1s.
A single binary data value (a 0 or a 1) is called a bit.
4 bits is called a nibble (e.g. 0101 or 1100).
8 bits is called a byte (e.g. 10101001 or 01011100).
There are two main measurement systems:
Metric Units of Measurement
The gap between units when using metric values (also known as the decimal system) is always 1,000. For example, there are 1,000 bytes in 1 kilobyte and 1,000 kilobytes in 1 megabyte.
To convert between metric units, divide by 1,000 when moving to a larger unit (e.g. 500 megabytes is 0.5 gigabytes) and multiply by 1,000 when moving to a smaller unit (e.g. 4.7 terabytes is 4,700 gigabytes).
For example, 8,520 KB is the same as 8.52 MB or 0.00825 GB.
Metric values (usually) have a prefix ending in ‘a’ such as megabyte or gigabyte.
Binary Units of Measurement
The gap between units when using binary values is always 1,024. For example, there are 1,024 bytes in 1 kibibyte and 1,024 kibibytes in 1 mebibyte.
To convert between binary units, divide by 1,024 when moving to a larger unit (e.g. 4,096 kibibytes is 4 mebibytes) and multiply by 1,024 when moving to a smaller unit (e.g. 55 pebibytes is 55,296 tebibytes).
For example, 34 KiB is the same as 34,816 MiB or 35,651,584 GiB.
Binary values have a prefix ending in ‘bi’, such as kibibyte or mebibyte.
Computer scientists often use the binary system of measurement because the storage size is technically more accurate.
Questo's Questions
1.7 - Units of Measurement:
1a. Create a table or list that clearly shows the relationship between values from bit up to petabyte for the metric (decimal) measurement system. [4]
1b. Create another table to display the binary measurement system from bit to pebibyte. [4]
2. Make the following conversions and show your working out. [2 each]
a. 40 megabytes into kilobytes.
b. 8500 gigabytes into terabytes.
c. 100 mebibytes into kibibytes.
d. 854,016 mebibytes into gibibytes.
e. How many bytes are there in 3 megabytes?
f. How many bytes are there in 3 mebibytes?