Unit 2 - Data representation Flashcards
Why is hexadecimal used instead of binary?
Binary
Mark scheme answer
- Easier/quicker to communicate / enter /write / read / remember
- Less chance of input errors // easier to spot errors
- They are shorter
- Easy to convert between binary and Hexadecimal
How can transistors be used to store a value in binary?
Binary
Mark scheme answer
- Transistor has two states
- 1 represents on, 0 represents off
- Each transistor stores one bit
- Multiple transistors used to store a binary value
Why do computers represent data in binary form?
Binary
Mark scheme answer
Computers consist of transistors / switches which only have values 1 or 0
What does a left shift do?
Binary
Multiply binary by 2
What does a right shift do?
Binary
Divide binary by 2
What are the 2 character sets?
Characters
- ASCII
- Unicode
What is ASCII?
Characters
American Standard Code for Information Interchange has become the standard code used globally. It uses a 7-bit binary code to encode 128 letters.
Why was Unicode developed?
Characters
ASCII is not enough to represent different languages and emojis, many more characters are needed.
For that reason Unicode was developed, including 16-bit or even a 32-bit to give over 4 billion combinations.
How is a character set used to represent a string?
Characters
Mark scheme answer
- Each character has a unique (binary) value
- Each character in the string is assigned its associated number/value
- The (binary) value of each character is stored
- Uses ASCII/Extended ASCII/Unicode
What are image file types?
Images
BMP
JPG
GIF
PNG
TIFF
Vector: SVG
What is a pixel?
Images
Pixels is the smallest identifiable area of an image, each pixel is given a binary value to represent it.
What is a bitmap image?
Images
Bitmap images are made up of pixels.
Resolution is the concentration of pixels within a specific area. It’s area is defined by the height and width of the image in pixels (PPI or DPI)
Each value in a pixel represents a certain colour.
What is bit depth?
Images
The more bits there are in a pixel, the more colour combinations there are.
Each pixel can only represent a specific number of colours, the combination is the bit depth in terms of 2^n (n being the number of bits). Higher bit depth gives a greater range of colour and a better quality of image.
How can increasing colour depth affect image?
Images
Mark scheme answer
- The quality of the image can be improved
- The file size will increase
- The number of colours that can be
represented/used will increase
How do you calculate bits required for an mage?
Images
Bits for image = Number of pixels x colour depth
What is a monochrome image?
Images
Monochrome images only use colour black (0) and white (1). They only store the binary value, the image dimension. You can change the colour by changing the binary value.
How does color work in an image?
Images
Each pixel has a proportion of red,green and blue to make up its colour. Colour values of individual pixels are expressed in software as denary RGB values and in hexadecimal. These are better to use as it is easier for people to read, write and remember and can reduce the errors when copied.
What is meant by the term image resolution?
Images
Mark scheme answer
- Number of pixels (in image)
- Height and width (of image)
What is metadata?
Images
Mark Scheme answer
Data about data / the image/file //
properties of the file
Examples of metadata of an image
Images
Height
Width
Colour/bit depth
Date
Geolocation
File size
File type
Compression type
Author
How are bitmap images are represented in binary?
Images
Marks scheme answer
Image made of / split up into pixels
Each pixel given a binary code which represents the colour of that pixel
Each colour is given a different/unique
binary code. Metadata stored alongside the image
How is an analogue sound wave is converted into digital form?
Sound
Mark scheme answer
- sound wave is sampled amplitude/height (of wave) is measured regular time intervals
- Each sample/measurement is stored as a binary number
- The binary number for each sample is stored sequentially
Why is analogue sound converted?
Sound
Sound must be converted into a digital form so the computer can process and store it. Sound wave has to be repeatedly measured and recorded to be digitised.
What is a sound sample?
Sound
Sound sample is measurement of amplitude of a sound wave area given time. Sound is sampled using the sample rate and bit depth.
