Download OCR GCSE (9-1) Computer Science Teacher Power Point 2.6 Data

Unit 2.6
Data Representation
Lesson 1 ‒ Numbers
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Starter
Put these units in the correct order of size
(smallest->largest):
• Bit
• Gigabyte
• Kilobyte
• Byte
• Petabyte
• Terabyte
• Megabyte
• Nibble
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Learning Objectives
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Define the units bit, nibble, byte, kilobyte,
megabyte, gigabyte, terabyte, petabyte.
Know how data needs to be converted into a binary
format to be processed by a computer.
Know how to convert positive denary whole
numbers (0-255) into 8 bit binary numbers and vice
versa
Know how to convert from binary and denary into
positive hexadecimal numbers (0-255) and back
again
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Units
The following units describe how much disk space,
capacity or data storage is used.
• Bit
• Nibble
• Byte
• Kilobyte
• Megabyte
• Gigabyte
• Terabyte
• Petabyte
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Introduction to binary
Unit 8 Data Representation
What is this symbol? Why?
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Introduction to binary
Unit 8 Data Representation
Creating a circuit
• Computers comprise billions of switches to turn
voltage on and off
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Introduction to binary
Unit 8 Data Representation
Representing values
• Consider the same byte value 0011 1001
• This is represented in denary as 57
• As an electrical circuit this could be represented as:
0
0
1
1
1
0
0
1
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Bit
• A 'bit' is a Binary Digit
• A Binary Digit is the smallest unit of data a computer
can store
• Each 'bit' is represented using either a 1 (true) or 0
(false)
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Nibble
• This is a less known term
• It describes a group of 4 bits
• A nibble is really useful when converting between
binary and hexadecimal
• A Nibble will only cover decimal numbers between 0
and 15
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Byte
• A 'byte' is a collection of 8 bits.
• It is the ‘building block’ for every other measurement
• Keyboard characters generally take up 1 byte (8
bits) of storage
• Every other storage measurement is made up from
multiples of bytes
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Kilobyte
• This is another common unit of measurements
• It can be written as kB or kbyte.
• A kilobyte can be thought of as 1,000 bytes
• However because we are counting in binary, it is
actually 1024 bytes
• You may use either in an exam!
• Kilobytes are often used when talking about
document file sizes
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Megabyte
• A megabyte is the other most common unit of
storage.
• It can be written as MB or mbyte.
• Like a byte, a megabyte can be thought of as either
1,000 or 1,024 kilobytes
• We also use megabytes to measure transmission
speeds on the web and also storage space on a CD.
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Gigabyte
• A Gigabyte is 1024 Megabytes
• Again you can also use 1,000 Megabytes for rough
calculations
• It can be written as GB or gbyte
• You must be careful NOT to use Gb - this used for
gigabit
• To give you an idea of storage sizes, 1 Gigabyte could
hold:
‒ Over 3,000 books
‒ 25% of a typical movie
• We often use GB to refer to hard drive sizes
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Terabyte
• Terabyte is written as TB
• This is 1,024 Gigabytes
• More and more hard disks are now measured in
Terabytes
• A Terabyte can store:
‒ Over 300 hours of video
‒ 1,000 copies of the Encyclopaedia Britannica
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Petabyte
• You write a petabyte as PB
• A Petabyte is 1024 Terabytes (again you can use
1,000 in exams)
• A Petabyte is a massive amount of storage. It could
hold:
‒ Over 2,000 years worth of songs, back to back
‒ 315 million photos (3MB each)
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Activity 1
Create a Poster that defines all of the different units of storage.
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Your poster must include:
An order to the units in how they are displayed
Definition of each unit
Examples of what could fit into that unit
Colour that makes the poster engaging
Stretch & Challenge
Research and Include a section on what comes after Petabyte
and what could possibly be stored with that capacity.
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