3_3_3 Units of information

You should be able to:

Know that:

•• a bit is the fundamental unit of information

•• a byte is a group of 8 bits.

Know that quantities of bytes can be described using prefixes.
Know the names, symbols and corresponding values for the decimal prefixes:

•• kilo, 1 kB is 1,000 bytes

•• mega, 1 MB is 1,000 kilobytes

•• giga, 1 GB is 1,000 Megabytes

•• tera, 1 TB is 1,000 Gigabytes.

REVISE:

The Basics

Note that the examiner will not deduct marks if you state that the data storage measurement is in "1024's" rather than "1000's". However, the AQA Specification states that 1 kilobyte is 1000 bytes so we will learn our conversions in this way.

You need to know:

1 bit is just a 1 or a 0
8 bits is a byte
1000 bytes is a kilobyte
1000 kilobytes is a Megabyte
1000 Megabytes is a Gigabyte
1000 Gigabytes is a Terabyte

The symbols for each measurement type are:

bit is b
byte is a capital B
kilobyte is a lowercase k with an upper case B...so... kB
Megabyte is all capitals MB
Gigabyte is all capitals GB
Terabyte is all capitals TB

To get from a bit to a byte we multiply by 8.

All of the other units of measurement, you multiply by 1000.

As long as you remember the order... bit, byte, kilobyte, megabyte, gigabyte, terabyte then you should remember the maths!

8 B B K M G T - can you think of a saying to help you with this?

8 Basket Ball Kicks Make Gaming Tough

Converting between the storage measures

Two numbers to remember are: 1000 and 8

There are 8 bits in a byte

There are 1000 bytes in a kilobyte

This means that to get from kilobytes to bits you need to perform this calculation:

NUMBER OF BYTES = (number of kilobytes * 1000)

NUMBER OF BITS = (number of bytes * 8)

Let's try an example...

"Convert 5 kilobytes to bits"

5 * 1000 = 5000 (bytes)

5000 * 8 = 40000 bits.

The answer is 40000 bits.

What about the other way?

If we have 40000 bits that need converting to kilobytes then we do this:

40000 / 8 = 5000 (bytes)

5000 / 5 = 1000 (kilobytes)

The answer is 5 kilobytes.

TEST:

Download and print the test paper here: https://drive.google.com/open?id=0B5fLtQ0Xgr2PZGoxV1c5TG1zVTQ
Try the mock test yourself.
Use the 3.3.3 Walking Talking Mock below to guide you through answering the questions.

SOURCE RECOGNITION - PLEASE NOTE: The examination examples used in these walking talking mocks are samples from AQA from their non-confidential section of the public site. They also contain questions designed by TeachIT for AQA as part of the publicly available lesson materials.

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