Data Types / Binary Flashcards Preview

A-Level Computer Science OCR > Data Types / Binary > Flashcards

Flashcards in Data Types / Binary Deck (61)
Loading flashcards...
1

primitive data type

a basic data type provided by the programming language as a basic building block

2

types of primitive data types (5)

- integer
- real/float
- boolean
- character
- string

3

denary

base 10 number. uses the combination of ten symbols to represent any number

4

binary

base 2 number. uses the combination of 2 symbols (0 or 1) to represent every number

5

hexadecimal

based 16 number. uses the combination of 16 symbols (10 numbers and 6 letters) to represent every number

6

why use hexadecimal?

- easier to read/ remember
- quicker to write/type
- less chance of making an error
- easy to convert

7

uses of hex

- define colours
- in MAC addresses
- in assembly language and machine code

8

integer

any positive or negative whole number e.g. 3, 0, -14

9

real (floating point)

a positive or negative number with a fractional component e.g. 0.002 or -1.98

10

character

Any single letter, symbol, number, character or control character

11

string

any combination of letters, symbols, numbers, characters or control characters e.g. Hello, £4.56

12

Boolean

Any true/ false data types which often represent logical situations

13

Sign magnitude most significant bit

represents + or -
+ = negative
- = positive

14

0.1

positive

15

1.0

negative

16

fixed point binary

positive of the binary point is fixed on the number line

17

by changing the position of the binary point you can...

increase the size of the number
increase the accuracy of the number

18

mantissa

the actual number you want to store

19

exponent

positive of the binary point is fixed on the number line

20

how to convert floating point binary to denary

1) First work out the denary number in the exponent which tells us that the binary point moves 'n' places to the right
2) Write out a new binary weighting line with the point in the right place and then convert into denary

21

Binary -> denary positive exponent

right

22

Binary -> denary negative exponent

left

23

in two's complement the sign is stored in

the most significant bit

24

normalising a number

means that there is only one way to represent the number

25

advantage of normalisation

it stores the most accurate version of that number.

26

Bitwise manipulation

bitwise shifts and masks

27

Bitwise shifts can be used ...

to change numbers quickly

28

Masks can be used ...

to set and toggle specific bits in a larger sequence.

29

toggle

swap to the opposite

30

What is bitwise manipulation useful for?

- Compression Algorithms
- networks (protocols. routing packets)
- multiplication and division

31

What does a bitwise left shift do?

multiplies the number by 2.

32

What happens to bits falling off the end on a bitwise left shift?

If any bits fall off the end it is just lost and the empty place on the left is replaced with a 0

33

What does a bitwise right shift do?

divides the number by 2.

34

What happens to bits hat fall off the end with a bitwise right shift

If any bits fall off the end it is just lost and you back fill with 1s

35

how does arithmetic (signed) right shift work?

shift everything to the right and backfill the space with 1s

36

how does circular shifting work?

you shift either way and the left over bit circles back around to the beginning.

37

What is a mask?

A mask allows you to isolate, extract, toggle and set bit values in a sequence of bits.

38

Bitwise ANDing ...

extracts a subset of the bits in a value

when the mask is a 1 it retains the value however when the mask is a 0 it outputs just 0s meaning only certain values are extracted.

39

Bitwise ORing ...

sets a subset of the bits in the value

you use 1s where you want to set values and 0s when you want to leave them alone

40

Bitwise XORing...

toggles a subset of the bits in the value

when you use a 1 the bianry is toggled/ switched around and 0s there is no impact

41

When is Bitwise ANDing useful?

useful for TCP/IP and routing

42

toggle a subset of bits

Bitwise XORing

43

set a subset of bits

Bitwise ORing

44

extract a subset of bits

Bitwise ANDing

45

What does ASCII stand for

American Standard Code for Information Interchange

46

What are the two most common character sets?

ASCII and Unicode

47

What are character sets needed for?

needed so that a document which is made on one computer is still readable on another computer. Computers can have more than one character set installed.

48

What is a more complex data type called?

composite types

49

array

allows you to store multiple items of the same data type under a shared common name

50

subtract binary numbers

two complement one and then add

51

how to twos complement a number

from right to left move until you hit a 1. all the subsequent bits should be swapped.

52

How are character sets used to represent text?

When character in the set has a corresponding binary value which is a set number of bits. These are stored in a sequence that represents a word etc.

53

more bits in the mantissa...

improves the accuracy but reduces the range

54

more bits in the exponent...

improves the range but reduces accuracy

55

how to normalise a number:

1. see how many places the binary point has to move so the number starts 01 or 10
2. store this number in the exponent and then new format of the number in the exponent

56

normalising a negative binary number

back fill with 1s at the high end and 0s at the low end

57

normalising a positive binary number

back fill with 0s

58

normalising:
moving the point to the right

- exponent

59

normalising:
moving the point to the left

+ exponent

60

why is twos complement better than sign magnitude

it easy to complete calculations with twos complement

61

How does the size of the mantissa and exponent effect the number

the larger the mantissa the more accurate
the large the exponent the larger the range of numbers that can be represented