Grade 8 WK 14 Calculating File Transfer Speeds .ppt

Calculating File Transfer Speeds
Bandwidth Bottlenecks

1. Program Requirements
Bandwidth : Bandwidth is the amount of data that can be
sent in 1 second, in bits per second.
Using the fiber optic example:
•on, off , on, off, on, off , on, off , on, off , on, off in 1
seconds
•12 bits in 1 second (6 on + 6 off)
•12 bps (bits per seconds)

2. Megabits and Mebibits of bandwdith
1 byte = 8 bits
1 kibibyte = 1024 bytes
1 mebibyte = 1024 kibibytes
1 kibibyte = 8192 bits ( 1024 x
8)
1 mebibyte =8388608 bits
(8192 x 1024)

3. Calculating File Transfer Speeds
File size = 120 KB
Bandwidth = 40KiB per second
File transfer speed = 3 seconds

4. Typical File Transfer Speeds
Bandwidth = 5MiB Bandwidth = 40MiB
2048 KiB Email attachment 2048 KiB= 2MiB
2/5 = 0.4 seconds
2/40= 0.05 seconds
15 MiB Audio File 15/5= 3 seconds 15 / 40 = 0.375 seconds
50 MiB Video Clip 50/5= 10 seconds 50 /40 = 1.25

5. Bandwidth Bottlenecks
When you download a file from the internet, you do not
have a direct connection to the original source of the file.
The file will pass through many different networks on its
journey.

6. Bandwidth Bottlenecks
When you download a file from the internet, you do not
have a direct connection to the original source of the file.
The file will pass through many different networks on its
journey.
Router 1 Router 2 Router 3
Users
Computer
25 MiB/s13 MiB/s 4 MiB/s 50 MiB/s

7. Program Requirements
It is possible to create a file transfer program in Scratch that
can calculate the time it takes for a file to download.
Following variables and functionality:
•File size
•Bandwidth
•Transfer Time

8. Scratch Example
•A welcome message is displayed
•The user is asked for file size in bytes
•The user is asked for the current bandwidth in bytes
•The file size value is divided by the bandwidth
•The resulting denary number is saved as transfer Time
and displayed on screen by the sprite

9. Calculating File Transfer Speeds
It is important to carry out testing on any program and
a test table is used to check the functionality of the
program.File Size
Input
Bandwidth Transfer
Time
Expected
Transfer
Time
Actual
Result
Changes
required
Retest
Result
120 30 4

10. Compression
Compression is simply the reduction of size of computer file.
There are two types of compression:
Lossy Compression
Lossless Compression

11. Reasons of Compression
•Attaching documents to emails
•Storing large files on a computer
•Transferring files on a storage device
•Speeding up download time of large files

12. Lossy Compression
•Lossy compression deletes part of the file,
reducing the file size, but when the file is
decompressed, the deleted parts cannot be
restored.

13. Lossless Compression
•Lossless compression prevents any data or
quality being lost when the file is compressed
and decompressed.

14. Image Compression Settings
•Following are adjusted when compressing an
image file.
•Colour Depth
•Resolution
•Image size

15. Run Length Encoding
RLE is a lossless compression method. It works by analysing
and reducing any repeated characters in a string by
grouping them together.
YYXXXXXXXYYYYYYYZZZZZZZZ
2Y7X7Y8Z

16. Run Length Encoding
RLE is a lossless compression method. It works by analysing
and reducing any repeated characters in a string by
grouping them together.
YYXXXXXXXYYYYYYYZZZZZZZZ 2Y7X7Y8Z
24 Bytes 8 Bytes

17. Image Data
•Requirement of:
•Image height and width in pixels
•The colour depth in bits

18. Compressing Image Data
bbbbbbw
bbwwwwb
bbwwwwb
bbbbbbw
bbwwwww
bbwwwww
Original Sting Size in Bytes RLE Version New size in Byes
bbbbbbw 7 6b1w 4
bbwwwwb 7 2b4w1b 6
bbwwwwb 7 2b4w1b 6
Bbbbbw 7 6b1w 4
bbwwwww 7 2b5w 4
bbwwwww 7 2b5w 4
Total file size 42 28

19. Cell Referencing
•Cell referencing allows
any piece of data,
across multiple
worksheets to be
referenced in a formula
or function.

20. Spreadsheet Formulas
Operators Description
+ Add
- Minus
/ Divide
* Multiply
= Equal to

21. Spreadsheet Formulas
Function Description
SUM Displays the total of a range of selected cells
AVERAGE Displays the average of a range of selected
cells
MIN Displays the lowest value in a range of cells
MAX Displays the highest value in a range of cells

22. Formulas and Functions

23. The effects of Technology on
environment
•The following are the major contributors to climate
change :
•Material Choices
•Energy Use
•Electronic Waste

24. Material Choices
•Increased use of technology means we need more
material to make them. Many of these materials are non-
renewable or very hard to recreate. For example:
•Precious material in circuit board such as gold and silver
•Sand , which is used to make glass and oil
•Aluminum, which used to create sleek product cases for
phones and other electronic devices

25. Electronic Waste (E-waste)
•E-waste describes devices that are no longer used and instead
of being recycled have just been dumped in landfill sites.
Problems caused by e waste include:
•Perfectly usable devices are not recycled
•Rare and toxic material can leak into the ground if devices are
not disposed properly
•Discarded electronics in landfill sites cab ve a health risk to
workers.

26. Preventing Environment Damage
Material Choices Energy Use Electronic Waste
•Reduce the need for rare
elements and focus or
artificial replacements
•Recycle the materials used
to manufacture devices
•Reduce the size and
thickness of devices
•Create more efficient
batteries that need less
charging and last longer
•Focus on renewable energy
sources such as solar and
wind
•Produce energy –efficient
devices that will hibernate
so that they save power
when not in use
•Create collection and
recycling points for
damaged /unwanted
devices
•Rehome unwanted devices
•Improve the upgradability
of devices, such as adding
memory rather than
replacing them

27. A B C D E
1Person Devices Total People =count(A2:A6)
201 3
302 2
403 1
504 5
605 3

28. A B C D
1 PersonOS Choice Number of Apple OS
2 01 Windows =COUNTIF(B2:B6,”Apple”)
3 02 Apple
4 03 Apple
5 04 Linux
6 05 Linux

29. Thank
you