[Unit 1.4.1] Data Types

Question 1

define data type

Answer 1

nature of data a variable can hold

Question 2

what do data types specify

Answer 2

kind of values that can be stored

what operations can be performed on them

how data is stored in memory

Question 3

why are data types important

Answer 3

error prevention

efficient memory use

performance optimisation

code clarity and maintainability

Question 4

what is the difference between data types and data structures

Answer 4

types - low level and intrinsic to variables

structures - high level and organise multiple variables

Question 5

define character code

Answer 5

unique binary sequence represent a single letter

Question 6

define character set

Answer 6

standardised collection of characters and their codes to represent them

Question 7

what is ASCII

Answer 7

American Standard Code for Information Interchange

originally used 7 bits. 128 combinations (0-127)

Question 8

what is extended ASCII

Answer 8

8 bits, 256 characters (0-255)

-additions were non-standard and varied between countries

Question 9

what are the disadvantages of ASCII

Answer 9

-256 values is not enough to represent all symbols for all languages of the world

-people made systems which were not compatible with each other

Question 10

define Unicode

Answer 10

Unicode is a standard character set that is backwards compatible with ASCII. uses 32 bits. standard across all systems

Question 11

features of a Array

Answer 11

Fixed size

Items can change

Can store only one data type

Question 12

features of a List

Answer 12

Can change size

Items can change

Can store more than one data type

Question 13

features of a Tuple

Answer 13

Fixed size

Items can’t change

Can store multiple data types

Question 14

what are unsigned values

Answer 14

integers have positive values

Question 15

what are signed values

Answer 15

integers can be positive or negative

Question 16

how does “sign and magnitude” work

Answer 16

uses MSB to determine if value is negative or positive
0 is positive
1 is negative

Question 17

what are the disadvantages to sign and magnitude

Answer 17

halves the highest value we can represent
complicates arithmetic

Question 18

how does twos complement work

Answer 18

MSB is a negative value (e.g in 8 bits the MSB would become -128)
thus:
0 is positive
1 is negative

Question 19

how do you convert from regular binary to twos complement (+ -> -)

Answer 19

write out the positive value
flip all the bits to the left of LSB (keep LSB same)

Question 20

what values can you represent in 8 bits using sign and magnitude

Answer 20

-127 to 127

Question 21

what values can you represent in 8 bits using twos complement

Answer 21

-128 to 127

Question 22

what are the rules for binary addition

Answer 22

0+0 = 0
0+1 = 1
1+1 = 0 (carry 1)
1+1+1 = 1 (carry 1)

Question 23

what are the rules for binary subtraction

Answer 23

0-0 = 0
0-1 = 1 (flip 0s till you get to 1)
1-0 = 1
1-1 = 0

Question 24

how can you do binary subtraction using twos complement

Answer 24

17-14 is the same as 17+(-14)
so switch 14 into twos complement
and do binary addition
ignore overflow

Question 25

what is bitwise manipulation

Answer 25

modifying data by changing bits within byte

Question 26

what does a shift to the left do

Answer 26

multiplies by 2

Question 27

what does a shift to the right do

Answer 27

divides by 2

Question 28

how can you multiply by 6 on a binary number

Answer 28

first multiply original value by 2 then multiply original value by 4 add these two values together

Question 29

how do you do arithmetic shift

Answer 29

same as binary shift just keep the MSB the same

Question 30

what is the logical operator for AND

Answer 30

2 inputs, a D, one output. both values must be true

Question 31

what is the logical operator for OR

Answer 31

2 inputs, spaceship, one output, either or both values must be true

Question 32

what is the logical operator for XOR

Answer 32

2 inputs, ), spaceship, one output, either but not both values must be true

Question 33

what is bit masking

Answer 33

keep, change or remove desired part of information by imposing a mask over its bits

Question 34

what are the 3 masks for bit masks in terms of bitwise manipulation

Answer 34

AND to extract OR to set XOR to toggle

Question 35

what is fixed point form

Answer 35

binary point in fixed position. does not need to be stored in memory

Question 36

what is floating point form

Answer 36

using mantissa and exponent.

Question 37

what is the function of the mantissa in floating point form

Answer 37

main number containing point after MSB

Question 38

what is the function of the exponent in floating point form

Answer 38

where binary point is positioned. if exponent is negative point goes left. if it is positive it goes right.

Question 39

what happens if you increase the amount of bits for the mantissa

Answer 39

increase in accuracy

Question 40

what happens if you increase the amount of bits for the exponent

Answer 40

increase in range

Question 41

define "normalisation"

Answer 41

moving binary point of decimal number

Question 42

why do we normalise numbers

Answer 42

to maximise accuracy and range for given number of bits

Question 43

how do you tell if a number is normalised

Answer 43

positive would start 01 negative would start 10

Question 44

how do you normalise a floating point

Answer 44

adjust exponent -move right (increase mantissa) decrease exponent -move left (decrease mantissa) increase exponent

Question 45

how do you convert from denary to floating point

Answer 45

write it in fixed point first in twos comp normalise write out fully

Question 46

how do you do addition/subtraction of floating point

Answer 46

normalise both numbers make exponents equal (smaller->larger) perform calculation normalise result