1.2.4 - Representing Flashcards
What is a Character Set?
A defined list of characters recognised by the computer, with each character represented by a unique binary number
What are the well known character sets? What’re the number of characters that can be represented?
ASCII - 7 bit set - 128
Extended ASCII - 8 bit set - 256
UNICODE - 24 bit set - >16mil
How are images stored?
In Binary, as either
Bitmaps :
- Constructed from coloured squares called pixels
- Each pixel of a bitmap is stored in binary
Vectors :
- Stores the maths to draw coloured shape
What are the number of bits required for a pixel?
Number required depends on the number of colours
- 1 bit has two values, so 1 bit can store two colours - black or white
- 2 bits have four values, so 2 bits can store four colours
- The number of bits for each pixel is the colour depth
What is Metadata?
- Additional data stored with the image to define the width, height, colour depth/palette
What is the effect on image size/quality when you change the colour depth/resolution?
- The greater the colour depth/res, the larger the file size
- The smaller the res, the lower the image quality
(pixels are larger in low res, less needed to fill the space)
How is sound sampled and stored in digital form?
- Analog sounds are converted to binary
- Sample rate - takes measures of sound waves at regular intervals
eg. CD sampled at 44100Hz = 44100 samples taken per second - Bit depth - affects the amount of info stored w each sample & helps the sound get as close to the original as possible
How is the playback quality of a sound file affected by
a) Sample Rate
b) Bit Depth
a) More samples, more accurate sound
b) Larger depth, higher quality sound
How is the size of a sound file affected by
a) Sample Rate
b) Duration
c) Bit Depth
a) The higher, the larger the file
b) Longer, larger file
c) The higher, the larger the file
