Unit 1.2 - text, sound and images Flashcards
What is ASCII code?
The American standard code for information interchange is the standard code used world-wide to represent characters in computer systems. Uses 7 bits to encode characters, meaning it can represent 128 characters including letters, numbers, punctuation symbols, etc.
What is Unicode?
Since ASCII can only represent 128 different characters and there are way more languages in the world, a new character set was developed called Unicode. Uses 16 bits, meaning it can represent 65,536 people.
What type of waves around sounds wave in the real world?
Analogue waves, which have to be converted into digital waves for the computer to be able to process them
What are digital waves made of?
Sequence of discrete signals; this is a complex series of on and off signals.
Name 5 types of sound files
- .MP3
- .ACC
- .FLAC
- .M4A
- MP4
What is sampling?
A task a computer performs to represent an analogue waves in a digital format.A computer takes regular measurements of the sound wave. Each measurment is saved as a binary number.
Which 2 things does a computer need to measure and record to perform sampling?
It needs to record how many bits used to record each measurement (sample resolution) and the number of measurements taken per second (sample rate).
What is the correlation between sample resolution and quality and file size?
The higher the sample resolution, the more accurate the sound is to the original recorded/better quality but the larger the file size.
What does the sample rate affect?
Otherwise called frequency, it affects the level of detail in digital sample/better quality. The more times the analogue wave is sampled, the more data is gathered. Greater frequency=greater file size.
What is sample rate/frequency measured in?
Hertz/kilohertz
How is an estimate for sound file size calculated?
Length (seconds) x sample rate (hertz) x sample resolution. Gives answer in bits.
Name 3 types of image files and the differences between them
- .GIF
- .JPG
- . PNG
They all use different encoding methods
What is the smallest identifiable piece on an image called?
Pixel. Each pixel has its own binary number which relates to a specific color.
What is image resolution?
The number of pixels within an image, normally described using the width and height of the image. For example : 1080 x 720
Higher resolution causes the image to be clearer but larger file size.
What is bit depth?
The number of bits per pixel. Increasing bit depth increases the amount of color combination. 1 bit per pixel - 2 colors; 2 bits per pixel - 4 colors, etc.
How is black and white written in hexadecimal?
White - #FFFFFF
Black - #000000
What is the difference between Bitmap and Vector graphics?
Bitmap images are collections of pixels. They will pixilate if zoomed into too much but most complex images have bitmap graphics.
Vector graphics are instructions on how to draw each shape. Good for simple graphics/shapes because they have smaller file size and have smooth rescaling.
How is an image file size calculated?
image resolution (image width x image height) x bit depth. Gives answer in bits.
