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?