8525 Unit 3

Question 1

Why computers use binary

Answer 1

Computers only understand 2 states: power on and power off
Represented by switches

Question 2

Bits, bytes, KB, etc

Answer 2

1 byte = 8 bits = 1 character of text
1 kB = 1000 bytes
1 MB = 1000 kB or 10^6 bytes
1 GB = 1000 MB
1 TB = 1000 GB

Question 3

2 major character sets used today

Answer 3

ASCII - 7/8 bit
Unicode - 16/32

Question 4

Bitmap image file formats:

Answer 4

BMP
JPG
GIF
PNG
TIFF

Question 5

Vector image file format

Answer 5

SVG

Question 6

What is a pixel

Answer 6

A pixel is the smallest identifiable area of an image
Each pixel is a single colour and is given a binary value with represents that colour

Question 7

Image resolution

Answer 7

Resolution is the concentration of pixels within a specific area

The area is defined by the image width and height in pixels e.g 1920 x 1080

Question 8

Creating an image with binary values

Answer 8

Each value represents a different colour

1 bit - 2 colours
2 bit - 4 colours
3 bit - 8 colours

Question 9

What type of compression do images mainly use

Answer 9

Lossy

Question 10

How does the number colours affect file size

Answer 10

An increase in the number of colours that are used in an image (the bit depth) will increase the file size

Question 11

How does the size of the image affect file size

Answer 11

An increase in number of pixels in the image will increase the file size

If an image’s physical size is increased by making each pixel larger then there is no change in the file size

Question 12

PBM monochrome images

Answer 12

Portable bitmap images
0 for white and 1 for black

Image dimensions are given in the first row
Image data is then given after

Question 13

Calculating image size

Answer 13

Size in bits = width x height x colour depth

Size in bytes = width x height x colour depth / 8

Question 14

Metadata

Answer 14

Data about data
In terms of images: colour depth, resolution, date created, author

Question 15

Analogue to digital converters

Answer 15

Sounds converted into a digital form in order to be stored and processed by a computer

Analogue to digital—converts inputs to digital signals

Digital to audio—is used to convert digital signals to outputs

Question 16

Sound sampling

Answer 16

Sampling rate = number of samples taken per second

Sample resolution = bit depth

Calculating sound file sizes:
File size = sampling rate x resolution x duration

Question 17

Digitised sound quality

Answer 17

Recording quality improves: the more frequently we sample the sound

Increasing the sampling rate means recording more data points—incr the bit rate improves the accuracy of each data point

Question 18

Hertz (cs)

Answer 18

How many samples per second

Question 19

Lossy compression (in terms of sound)

Answer 19

Removes sounds that we can’t easily hear or that least affect the perceived playback quality

Question 20

Lossless compression

Answer 20

Reduces the file size when compressed but do not lose any information
Lossless music file formats:
FLAC
ALAC
W MA lossless

Question 21

Lossy compression

Answer 21

Permanently loses some data—cannot be decompressed

Question 22

Lossless image compression

Answer 22

Will not lose any of the original data

Question 23

Run length encoding (RLE)

Answer 23

Uses frequency/data pairs to encore each run length of the same coloured pixel
For example:
1 = white, 0 = black
1111000000000000

Using rle:
4 1 12 0

Question 24

Lossless text compression:

An eye for an eye, a tooth for a tooth

Answer 24

Uses repeated pattern in a dictionary
Example:
An eye for an eye

An eye for an eye, a tooth for a tooth.
. 0 0000
An_ 1 0001
eye 2 0010
for 3 0011
an_ 4 0100
,_ 5 0101
a_ 6 0110
tooth 7 0111
1 2 3 4 2 5 6 7 3 6 7 0

38 characters including spaces = 38 bytes

Assuming 8 bit ASCII: 38 characters = 38 bytes

Compression: 12 numbers used—> 6 bytes (each number was a nibble)

Question 25

Why is compression good

Answer 25

download times are reduced
Data allowances go further
It is possible to transmit video and music data streams as fast as they are playing
Faster to transfer

Question 26

benefits of compression

Answer 26

Smaller fillies = fewer packets = faster transmission time:
- quicker to complete transmission
- reduces traffic over the internet

reduces download times of video, sound (including speech used for VOIP systems) and I mage files:
- streaming is also possible as the data can be sent as fast as the rate it is played

Images inside web pages appear faster
Reduces space on disk/servers