Topic 3 - Data Representation and boolean Logic

Question 1

what is an overflow?

Answer 1

• when a result requires more bits than the CPU is expecting
• computers usually store extra bits elsewhere

Question 2

problems caused by overflow errors

Answer 2

• loss of data and accuracy in answer
• could cause software to crash if it doesn’t have a way of dealing with extra bit

Question 3

left binary shifts

Answer 3

• moves every bit to the left a certain number of places
• multiply a binary number x2 every place shifted

Question 4

right binary shifts

Answer 4

• moves every bit to the right a certain number of places
• divides a binary number by 2 every place shifted

Question 5

hexadecimal

Answer 5

• base 16 number system
• each digit represents 4 bits or a nibble

Question 6

advantages of using hexadecimal

Answer 6

• easier to remember large numbers as they are shorter than binary numbers
• shorter, less chance of input errors
• easier to convert from hex to binary

Question 7

what are character sets?

Answer 7

• a collection of characters a computer recognises from their binary representation

Question 8

ASCII

Answer 8

• each character is given a 7 bit binary code
• can represent 128 different characters which includes all letters, numbers, etc in English alphabet

Question 9

Unicode

Answer 9

• it covers every possible character that might be written
• uses multiple bytes for each character and covers all major languages
• first 128 codes same as in ASCII : compatible

Question 10

how are images stored?

Answer 10

• stored as bitmap images made up of tiny dots called pixel
  -each pixel is represented by a binary code

Question 11

colour depth

Answer 11

• number of bits used per pixel
• total number of colours =
  2ₙ , where n = colour depth
• greater colour depth = greater range of colours which makes the image more realistic and life-like

Question 12

resolution

Answer 12

• number of pixels in the image
• measure in DPI : dots per inch
• greater resolution, more pixels which makes the image look sharper
• increases quality of image

Question 13

impact of increasing both

Answer 13

• increases file size
• takes up more space on secondary storage

Question 14

how is sound stored

Answer 14

• sound recored by microphone as an analogue signal
• converted to digital data by A-D converters so computers can read and store sound files

Question 15

sample rate

Answer 15

• how many samples are taken per second
• analogue recording sampled more often
• ## better quality and match original sound more closely

Question 16

bit depth

Answer 16

• how much bits available per sample
• larger bit depth = larger range of sounds
• it can pick up quieter and louder sounds, closer quality to original sound

Question 17

compression

Answer 17

• reducing the size of a file