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Units and file sizes

File Sizes

Talking about file sizes – BYTES

Bytes – File Sizes, Memory Sizes
Nibble 4 bits (Only need to know this for the exam)
Byte B 8 bits
Kilobyte KB 1000 Bytes
Megabyte MB 1000 Kilobytes 1,000,000 Bytes
Gigabyte GB 1000 Megabytes 1,000,000,000 Bytes
Terabyte TB 1000 Terabytes 1,000,000,000,000 Bytes

When we are talking about file sizes we usually use Bytes as our basic unit.

For a example:

  • A text file is 25KB
  • A photo is 4.5MB
  • A computer game is 234GB

We use the same metric system as in normal maths – kilo, mega, giga, etc with each being 1000 times large than the previous one.

If you converting from one unit of bytes to the next you just either times by 1000 or divide by 1000.

Example:

  • 2MB = 2,000KB = 2,000,000 Bytes
  • 1,450MB = 1.45GB

Networking Speeds

Talking about network speeds / download speeds – BITS

Bits – Network / Data Transfer Speeds
bit b 1 bit
Kilobit Kb 1000 Bits
Megabit Mb 1000 Kilobits 1,000,000 bits
Gigabit Gb 1000 Megabits 1,000,000,000 bits
Terabit Tb 1000 Gigabits 1,000,000,000,000 bits
Usually expressed as a speed
E.g. 20Mb/s – 20 Megabits per second transfer speed

Most manufacturers talk about transmission speeds using bits not bytes

Conversions

Converting from bits to bytes

If you want to convert from bits to bytes, you simply divide the number of bits by 8

64 bits = 8 bytes

 

Converting from bytes to bits

To convert from bytes to bits you simply multiply the number of bytes by 8

2,000 Bytes  = 16,000 Bits

Crossword


1. 1000 Bytes
2. 1,000,000 Bits
3. 1,000,000 Kilobits
4. 1,000,000 Kilobytes
5. Used for storage and memory
6. Used for transmission speeds
7. Most appropriate unit for a smartphone photo
8. 1000 bits
9. 4 bits

Quiz

Practice Quiz

Resources

Resources

Past Paper Exam Questions

0478/11 – Paper 1 Theory May/June 2017 – Qn 1

0478/12 – Paper 1 Theory February/March 2017 Qn 13b

0478/11 – Paper 1 Theory October/November 2017 qn 2

0478/11 – Paper 1 Theory October/November 2017 qn 9b

0478/12 – Paper 1 Theory October/November 2017 Qn8a

0478/12 Paper 1 Theory February/March 2018 Qn9

0478/12 Paper 1 Theory May/June 2018 Qn 1

0478/11 Paper 1 Theory October/November 2018 Qn 1B