Data Flashcards
What are the place value powers?
Powers of 2
e.g. 2^0, 2^1, 2^2
What is an overflow error?
When a calculation produces a result that is greater than the computer can deal with
Binary addition rules
0 + 0 = 0
1 + 0 = 1
1 + 1 = 0 (carry 1)
1 + 1 + 1 = 1 (carry 1)
Logical shift rule
Move the bits as many times as specified and replace empty spaces at start/ end with 0s
What is SIGN AND MAGNITUDE?
The leftmost bit is used to signify whether the number is positive or negative
0 = positive
1 = negative
What is TWO’S COMPLEMENT?
Leftmost bit signifies whether the number is positive or negative
0 = positive
1 = negative (-128)
Replace the positive binary value 0s with 1s and vice versa and add 1 to find the two-s complement version
How do you multiply signed binary numbers?
Use an arithmetic shift left (every shift multiplies by powers of 2)
What is the rule with arithmetic shifts?
The most significant bit remains
e.g. a right shift by 2 of 10100101 = 11101001
How do you divide signed binary numbers
Use an arithmetic shift right (every shift divides by powers of 2)
Order of HEX values
1, 2, 3, 4, 5, 6, 7, 8, 9, A (10), B (11), C (12), D (13), E (14), F (15)
How do you convert hex values to binary?
1) Split up the characters
2) Each character is represented by a number in denary
3) Each denary value can be written as a nibble
4) Join the nibbles together
e.g. C3 –> 12 = 1100 and 3 = 0011 SO 11000011 is C3
What is ASCII?
Numbers assigned to text and characters using binary
What is EXTENDED ASCII?
Uses 8 bits so that there are 256 code sequences
- Previously used 7 bits
What is UNICODE?
Alternative to ASCII for other languages
An international encoding standard for use with different languages and scripts, by which each letter, digit, or symbol is assigned a unique numeric value that applies across different platforms and programs
What is a PIXEL?
Short for ‘Picture Element’
The smallest single point of colour in a graphic image
How do you work out IMAGE SIZE?
Total number of pixels
SO: number of pixels in width X number of pixels in height
What is RESOLUTION?
The number of pixels per inch when the image is displayed
What is COLOUR DEPTH?
The number of bits used to encode the colour of each pixel
The more bits used to encode colour, the greater the number of actual colours that can be represented
e.g. 1 bit = 2 colours (2^1), 8 bits = 256 colours (2^8)
How do you calculate IMAGE FILE SIZE?
File size (bits) = width X height X colour depth
What is a BITMAP image?
Organised grid of coloured squares called pixels
When zooming in or enlarging a bitmap image, the pixels are stretched and made into larger blocks
Appear as poor quality when enlarged too much
What is a VECTOR image?
Use scalable shapes such as straight lines and curves, using coordinates and geometry to precisely define the parts of the image
It is more efficient than bitmaps at storing large areas of the same colour because it does not need to store every pixel as a bitmap does
Vector graphics can be scaled without losing resolution
What is METADATA?
Data that describes other data
Name a LOSSLESS image data compression
PNG
It is often used where the graphic might be changed by another person or where the image contains layers of graphics that need to be kept separate from each other
It is high quality
Name a LOSSY image data compression
JPEG
It is often used for digital camera images because it has a fairly small file size for the quality that it displays
Higher compression rate than PNG in the trade-off for quality
