Chapter 9 Flashcards
Define character set
A list of binary codes used by a computer to represent characters (eg. Text)
What is ASCII and what does it stand for?
A character set
American Standard Code for Information Interchange
How many unique characters could the original ASCII represent?
2^7 = 128
How many bits were used in the original ASCII?
7
What do the first 32 binary codes represent?
Formatting commands
How to convert from ASCII to character in python
Chr()
How to convert from character to ASCII?
Asc()
Why was extended ASCII created and how many bits are used?
8 bits because computers think in a byte and it allows for more characters. - 2^8
What is and why was Unicode created.
- Different companies used different character sets so a universal code was needed
- 256 codes were not enough
- Unicode uses 4 bytes and can represent 2^32 characters
Why was ASCII created?
To make a universal code so all devices could understand each other.
How are pictures stored digitally?
Stored as a bitmap - broken down into pixels. Each pixel colour is encoded into binary
What is colour depth?
The number of bits used to encode the amount of red green and blue in each pixel.
What is the total no of shades a colour depth can represent?
2^no bits
How to find image file size
File size = pixel width x pixel height x colour depth/bits
What is Metadata
Extra data about the file such as:
Resolution
Any edits
Owner
Date and time
Disadvantages of analogue recordings
Difficult to transport
Can degrade
Hard to edit + copy
Limited storage
Advantages of digital recordings
Easy to transport
Does not degrade
Cheap to edit+copy
Thousands of songs can be stored in a hard drive
How are audio files recorded?
sound waves amplitude was sampled thousands of times a second and encoded into binary
How to increase quality of a audio file?
Increasing the sample rate - the no of samples taken per second
Increasing Bit depth - the no of bits used to represent each sample
What is the normal sample rate?
44.1KHZ
How to calculate an audio file size
Audio file size = sample rate x bit depth x no. Channels x length/seconds
How to increase resolution of an image
Increase no. Pixels
Name 2 types of compression
Lossy
Lossless
Define lossy compression
Decreasing file size by removing data. The data is not recoverable.
