Topic 3-Data representation Flashcards
What do computers use to represent all data and instructions?
Tiny switches called transistors and electric circuits.
What are binary digits?
Bits, a nibble is 4 bits.
What are hexadecimal used for?
They provide a human friendly representation of binary values and are quicker to write and type. It is also less likely for humans to make mistakes.
What are binary shifts and how can they be used?
They can be used for simple division and multiplication and each number that goes out is discarded.
What is largest number 5 bits can represent?
31 but it can do 32 letters.
Why was ASCII created?
To standardise communication. 7 bits so 128 characters.
Why was unicode created?
So not only the English language could be represented. Uses 4 bytes so around 138,00 characters. The first characters were the same as ASCII so old systems did not have to update.
What is a picture element?
A pixel is the smallest element in an image.
What is a group of pixels together called?
A bitmap.
What is resolution?
The total number of pixels.
What is colour depth?
A colour depth of 3 can store 8 colours for one pixel.
What is RGB?
Used to combine light for more in depth pictures. 24 bits per colour so 8 for red, 8 for green and 8 for blue. This allows 256 colours. Charlie loves RGB.
What are the types for bitmap images?
.JPG, .PNG, .BMP AND .TIFF
How do you calculate the file size of an image?
Resolution x colour depth
What are vector graphics?
Creating an image with vector coordinates(pixels can not always be seen).
What are the pros and cons of vector graphics?
+can never see pixels
+smaller file size for same image
+amazing for simple, small or large images
-terrible for realistic images
What is analogue sound?
Sound waves travel through vibrations in the air.
What is the amplitude?
The height of the sound wave. The higher the amplitude, the higher the sound.
What is the pitch?
Closer together waves means higher pitch and frequency.
What is an ADC?
Analogue to digital converter.
What is a sample rate?
Number of measurements taken per second(Hz).
What does the bit depth mean for sounds?
Higher bit depth means higher resolution of sound.
How do you calculate file size for sound.
seconds x bit depth x sample rate
What frequency can babies hear?
20-20,000.
What protocol does facetime use?
Voice over internet protocol(VOIP).
What is MIDI?
Digital interface for sound that is more consistent and can represent music with instructions. Notes do not fade.
What is metadata?
Data about data.
Why are files compressed?
To reduce download and upload speed for faster transmission and less data errors.
What is lossy compression?
Removes useless information such as frequencies humans cannot hear or a shade we won’t notice. 10-2-6. File cannot be fully restored.
What is losless compression?
No data is lost. Done by RLE(run length encoding) or huffman trees(not always good as huffman tree has to be sent too). 10-4-10.
RLE example. 1101000
0011110
21 10 11 30
20 41 10
What side is 0 on for huffman trees?
Left.
