Computing#4-Data Representation

Question 1

Logic gates

Answer 1

And, Or, Not.
And-both inputs must be on(1)
Or-Only one input needs to be on(1)
Not-Switches the input(eg. If input is 1, it becomes 0, vice versa)
2-level logic circuits are circuits in which inputs must pass through a maximum of 2 logic gates to reach the output.

Question 2

State units for digital information

Answer 2

Bit(b)-single binary digit(1 or 0)
Nibble-4 bits
Byte(B)-8 bits
Kilobyte(KB)-1024 bytes
Megabyte(MB)-1024 Kilobytes
Gigabyte(GB)-1024 Megabytes
Terabyte(TB)-1024 Gigabytes
Petabyte(PB)-1024 Terabytes
Exabytes(EB)-1024 Petabytes
Zettabytes(ZB)-1024 Exabytes
Yottabytes(YB)-1024 Zettabytes

Question 3

Binary numbers

Answer 3

Our number system is called Denary. We can convert between denary and binary by drawing a table starting with 1 and keep doubling. This can count any number. Start at the left, and subtract the number in each column until your number is converted to binary

Question 4

Logic

Answer 4

Logic consists of Logic gates which are special circuits built into computer chips. These can combined for complex operations.

Question 5

Info about units of data

Answer 5

A byte can store a character
Most files such as songs pictures and docs are measured in kB or MB
High def vids and complex apps are often measured in gigabytes
Secondary storage is measured in gigabytes or terabytes

Question 6

Hexadecimals

Answer 6

Multiplication tables for go up in powers of 16 from right to left, eg, 4096,256,16,1
Hex values go from 0-9 then 10-15 is A-F.

Question 7

Hex

Answer 7

Hex uses 16 different digits to represent 0-15. This can be represented by 4 bits in binary, so each hex is a nibble. To convert from binary to hex just split it into nibbles and assign.

Question 8

Characters

Answer 8

Alphanumeric letters are used to make words and strings
Computers can’t interpret these, so it uses character sets.
When you click a keyboard, it sends a series of binary signals which the computer translates using a character set.
ASCII and Unicode are standard more.

Question 9

ASCII

Answer 9

Commonly used character set. Assigns 7 bit binary code to each ASCII character. This creates 128 different characters. Each code has a big added to the front( a 0) so each character fits nicely into a byte. It’s main purpose is to parity check.
Letters and numbers are ordered(each decimal number assigned increases by one, this how u identify other ASCII characters when only given one), while symbols are scattered.

Question 10

Unicode

Answer 10

Covers ever possible character that might be written. It uses multiple bytes for each character. First 128 codes are identical to ASCII.

Question 11

Why do we compress files

Answer 11

Compression is when files are made smaller while making the compressed file as true to the original.
Uses:
Smaller files take less storage
Streaming takes less time as it takes lower bandwidth
Allows webpages to be loaded quicker
Email services have restrictions on file size sendable, compression allows it to still send the file.

Question 12

Lossy compression benefits

Answer 12

Reduced file size
Less bandwidth(amount of data that can be transferred on a network in a given time)
Commonly used-many software can read lossy files

Question 13

Lossy compression cons

Answer 13

Loses data, file won’t be the same as original

Can’t be used on software or text files as these need to retain all the info of the original

Question 14

Types of lossy compression

Answer 14

MP3(audio)
AAC(audio)
JPEG(image)

Question 15

Lossless compression

Answer 15

Does not remove the data permanently, only removed temporarily, no reduction in quality so compressed file should look and sound like the original.
Can be decompressed
Can be used on both text and image files.

Question 16

Lossless cons

Answer 16

Slight reduction of size, but they still take a lot of space on devices.

Question 17

Types of lossless compression

Answer 17

FLAC(audio)
TIFF(image)
PNG(image)

Question 18

Run length encoding

Answer 18

It is a way of lossless compression. Just count number of times occurred then colour. This creates a data pair. A pair consists of a 8 bit number to represent the times repeated, and an 8 bit colour. This creates 16 bits per pair. This is for pictures.

Question 19

Run length coding for text

Answer 19

The string wwwwwhtttt
Here we can see 5,w 1,h and 4,t. ASCII can store characters as a byte, so this will be stored as 6 bytes instead than the full 10 bytes.