## 1.7 - Units of Measurement

## Exam Board:

## OCR

## Specification:

## 2016 - Unit 1

All computer systems communicate, process and store data using binary.

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Binary is a number system consisting entirely of 0s and 1s.

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A single binary 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 01011100).

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There are two main measurement systems:

## Metric Units of Measurement

The metric system is also known as the decimal system.

Metric values (usually) have a prefix ending in ‘a’ such as megabyte or gigabyte.

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The gap between units is always 1,000. For example, 1,000 bytes in a kilobyte and 1,000 kilobytes in 1 megabyte.

## Binary Units of Measurement

Binary values have a prefix ending in ‘bi’ such as kibibyte or mebibyte.

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The gap between units is always 1,024. For example, 1,024 bytes in a kibibyte and 1,024 kibibytes in 1 mebibyte.

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Computer scientists use the binary system of measurement because the storage size is technically more accurate.

## Questo's Questions

1.7 - Units of Measurement:

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1. a. How many bits in a nibble?

b. Put the following values in order from largest to smallest: MiB, TiB, PiB, KiB, GiB

c. How many gigabytes make a terabyte?

d. How many tebibytes make a pebibyte?