Flashcards in Data Types / Binary Deck (61)

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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

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## denary

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

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## binary

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

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## hexadecimal

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

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## why use hexadecimal?

###
- easier to read/ remember

- quicker to write/type

- less chance of making an error

- easy to convert

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## uses of hex

###
- define colours

- in MAC addresses

- in assembly language and machine code

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## integer

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

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## real (floating point)

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

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## character

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

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## string

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

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## Boolean

### Any true/ false data types which often represent logical situations

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## Sign magnitude most significant bit

###
represents + or -

+ = negative

- = positive

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## 0.1

### positive

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## 1.0

### negative

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## fixed point binary

### positive of the binary point is fixed on the number line

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

###
increase the size of the number

increase the accuracy of the number

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## mantissa

### the actual number you want to store

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## exponent

### positive of the binary point is fixed on the number line

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## 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

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## Binary -> denary positive exponent

### right

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## Binary -> denary negative exponent

### left

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## in two's complement the sign is stored in

### the most significant bit

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## normalising a number

### means that there is only one way to represent the number

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## advantage of normalisation

### it stores the most accurate version of that number.

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## Bitwise manipulation

### bitwise shifts and masks

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## Bitwise shifts can be used ...

### to change numbers quickly

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## Masks can be used ...

### to set and toggle specific bits in a larger sequence.

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## toggle

### swap to the opposite

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## What is bitwise manipulation useful for?

###
- Compression Algorithms

- networks (protocols. routing packets)

- multiplication and division

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## What does a bitwise left shift do?

### multiplies the number by 2.

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## 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

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## What does a bitwise right shift do?

###
divides the number by 2.

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## 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

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## how does arithmetic (signed) right shift work?

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

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## how does circular shifting work?

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

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## What is a mask?

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

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## 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.

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## 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

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## 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

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## When is Bitwise ANDing useful?

### useful for TCP/IP and routing

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## toggle a subset of bits

### Bitwise XORing

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## set a subset of bits

### Bitwise ORing

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## extract a subset of bits

### Bitwise ANDing

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## What does ASCII stand for

### American Standard Code for Information Interchange

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## What are the two most common character sets?

### ASCII and Unicode

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## 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.

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## What is a more complex data type called?

### composite types

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## array

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

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## subtract binary numbers

### two complement one and then add

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## how to twos complement a number

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

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## 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.

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## more bits in the mantissa...

### improves the accuracy but reduces the range

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## more bits in the exponent...

### improves the range but reduces accuracy

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## 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

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## normalising a negative binary number

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

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## normalising a positive binary number

### back fill with 0s

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##
normalising:

moving the point to the right

### - exponent

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##
normalising:

moving the point to the left

### + exponent

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## why is twos complement better than sign magnitude

### it easy to complete calculations with twos complement

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