Computer Science Unit 1

How do computers represent data?

Text, images, audio, numbers

What is a bit?

A bit is one digit

What is a byte?

Eight bits

What is the formula for finding the highest number you can make with a certain number of bits

2^number of bits -1

What is the formula for finding the total number of numbers you can make with a certain number of bits

2^number of bits

What is digital data?

data that changes discreetly through a finite set of possible values

What is analog data?

data with values that change continuously or smoothly overtime?

What are the layers of abstraction?

Text

ASCII

Binary

What are the layers of abstraction for colored images?

Digital image layer

Sampling layer

Pixel layer

Binary layer

What is overflow error?

an error from attempting to represent a number that is too large.

• You can add an extra bite to left, but if it is fixed, you cannot add anymore.

What is round off error?

error from attempting to represent a number that is too precise the value will be rounded.

• Only some numbers are too precise

  • 0.76 0.16 0.33

• but there are some numbers that you can represent

  • 2^-1 2^-2

what is sampling pixels to create images?

a process for creating a digital representation of analog data by measuring the analog data at regular intervals called samples

• you either add or don’t add light into a pixel

What is Lossy compression?

a process for reducing the number of beds needed to represent something in which some information is lost or thrown away the process is not reversible

When is it best to use to use Lossy compression?

• file time is concern

• Needs to be sent in reasonable amount of time

• Multimedia

• Faster

Lossless compression

A process for reducing the number of bits needed to represent something without losing any information. This process is reversible.

When should you use lossless compression?

• Text

• Key of dictionary to reconstruct the original

• Accuracy is important

Creative commons

Free copyright licenses. You tell which ones you are fine with people using

Copyright law

• Benefits for artists and creator

  • Control over work

    • Economically

    • Decide where sold and how much

• Incentive to produce more work

• Others can’t copy

• You automatically own it