9618 Computer Science : Information Representation

Largest 8 Bit Binary

1 1 1 1 1 1 1 1

Smallest 8 Bit Binary

0 0 0 0 0 0 0 0

What is 218 in Hexadecimal

218 is 1 1 0 1 1 0 1 0 in binary

1 1 0 1 = 13 = D

1 0 1 0 = 10 = A

So, 218 = DA

4 uses of hexadecimal

1. HTML color codes

2. Mac addresses

3. Memory dumps

4. Error messages

What is an overflow error?

Occurs when a computer tries to store a value that is bigger than the number of bits available.

What is BCD

Binary Coded Decimal is a method of representing single decimal digits as 4-bit binary.

What are some uses of BCD

Digital time display

On-screen calculator

Currency values

Advantages of BCD

Simple for humans to represent large denary values in digital form compared to binary.

Disadvantages of BCD

The range of values is lower as it can only represent the denary values 0-9.

What is 394 in BCD

394 is 3 9 4

3 = 0 0 1 1

9 = 1 0 0 1

4 = 0 1 0 0

So, 394 in BCD = 0 0 1 1 1 0 0 1 0 1 0 0

What is 572 in BCD

572 is 5 7 2

5 = 0 1 0 1

7 = 0 1 1 1

2 = 0 0 1 0

So, 572 in BCD is 0 1 0 1 0 1 1 1 0 0 1 0

What is encoding

A process that turns analogue data into binary code

What is compression?

A process where a file's size is reduced to make it smaller. Files that have been compressed may need to be decompressed in order to be opened.

What are some benefits of compression?

1. Can help reduce the storage size needed to store the file

2. Quicker transfer times to upload/download the file.

3. Reduce the bandwidth needed to transfer the file on the internet.

4. Take less time to transmit the file directly between devices.

What is lossy compression?

Lossy compression uses an algorithm to automatically identify and remove redundant data like Sound frequencies humans can't hear, Shades of color that humans can't see.

What are the features of lossy compression?

Reduces file size by a lot

Images/sound can be of similar quality

Original file can't be recreated

Original file can't be recovered

Images are compressed by reducing the color depth or the resolution

Text files can't use lossy compression as loss of letters or words will make the text meaningless

What is lossless compression?

lossless compression uses an algorithm to group together identical colors and sounds.

Doesn't reduce the file size by a lot

Any data removed can be recovered

What are the features of lossless compression?

In images, identical colors are grouped together

In Sound files, sections of identical sounds are grouped together

original file can be recreated

What is RLE?

Run length encoding is a lossless compression method where an algorithm identifies runs of pixels with the same color. It records the color and the length of each run.