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computer science > Unit 3 > Flashcards

Unit 3 Flashcards

1
Q

Compression Definition

A

Compression reduces the storage space of files.

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2
Q

What is a natrual number?

A

Any positive integer

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3
Q

What is a whole number?

A

Any integer

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4
Q

What is a rational number?

A

Anything that can be expressed as a fraction

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5
Q

What is an irrational number?

A

Endless, cannot be expressed with a fraction or rounded

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6
Q

What are real numbers?

A

Rational or irrational numbers as long as there not imaginary

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7
Q

What are ordinal numbers?

A

Numbers which describe the numerical position of objects

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8
Q

What are cardinal numbers?

A

Natural numbers or positive integers used for counting

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9
Q

Why is hexidecimal used?

A

Easier to read than binary digits as well as being quicker to type or write, meaning less room for error

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10
Q

When is hex used?

A

Used to define colours, MAC addresses, assembly languages, and machine code

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11
Q

What is a bit?

A

A bit is the fundamental unit of information in the form of either a single 1 or 0.

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12
Q

What do bits represent?

A

A bit represent electronic states either on (1) or off (0)

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13
Q

How many bits are in a byte?

A

8

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14
Q

What is ASCII?

A

A seven bit character encoding standard used the cover the charactersitcs of an american english keyboard.

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15
Q

What is extended ASCII?

A

An 8 bit version of ASCII which included an additional 128 characters to make it a bit more global.

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16
Q

What is unicode?

A

Unicode (UTF-16) is a 16 bit character encoding standard used to represent 65536 combinations of bits to represent dozens of languages.

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16
Q

Why would unicode not be used?

A

Takes up more space than ASCII which increases the file sizes and transmission times

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17
Q

Why is error checking needed?

A

Bits can change erroneously during transmssion owing to interference.

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17
Q

What is a parity bit?

A

A parity bit is an additional bit used to check whether the other bits transmitted are likely to be correct.

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17
Q

How does a parity bit work?

A

An odd parity bit works by adding the bits in the transmission together, the parity will make it so that there is an odd number of 1s in the transmission. If there is an even number when it reaches the end stage, then there is an error

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18
Q

What are the different types of parity bits?

A

Even and odd

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18
Q

What is majority voting?

A

It is a system where each bit is sent 3 times so that if one of them is erroneously flipped, overall the data is still known as it is assumed that only one flipped

19
Q

What is a negative of majority voting?

A

Triples the volume of data that is being sent

20
Q

What is a checksum?

A

A math algorithm that is applied to a unit or packet of data to create a checksum value before the transmission, after transmission this is checked and if they are equal the transmission is deemed to be succesuful

21
Q

Why are floating point binary numbers used?

A

Allows larger and smaller numbers to be represented

22
Q

What is normalisation?

A

The process of moving the binary point of a floating point number to provide the maximum level of precision for a given number of bits

23
Q

Can all fractions be represented in binary?

A

No fractions such as 1/3 or 0.1 cannot which means no matter how large the mantisa is, some accuracy will be lost

24
Q

Advantages of Floating Point

A

Allows for a greater range of numbers using the same number of bits

25
Q

Advantages of fixed point numbers?

A

Simple and faster to process, the precision of numbers depends on the binary point

26
Q

What is underflow?

A

Underflow occurs when a number is too small to be represented in the allotted number of bits, if a small number is divided by a large number, it may round to 0

27
Q

What is overflow?

A

Overflow occurs when the result of a calculation is too large to be held in the number of bits allocated

28
Q

What does a bitmap image contain?

A

Contains many picture elements that make up the whole image

29
Q

What is a pixel?

A

A pixel is the smallest identifiable area of an image, each pixel is attributed a binary value whitch represents a single colour

30
Q

What is the equation for the resolution?

A

Width in pixels * height in pixels. Note: this is not the size of the image only the number of pixels in it/

31
Q

How else can resolution be expressed as?

A

PPI: Pixels per image indicates the density of the pixels

32
Q

What is DPI?

A

Dots per Inch and is a printing term relating to the number of dots on a page

33
Q

What is the colour depth?

A

The number of bits per pixel, the higher the colour depth, the more colour combinations are possible

34
Q

What is metadata?

A

The data about data? The data about the image possibly including where it was taken, when etc

35
Q

What are vector images made of?

A

Vector images are made up of geometric shapes or objects rather than manipulating individual pixels

36
Q

What does a vector file store?

A

Only the necessary details about a shape in order to redraw it: for example to recreate an image of a circle a computer must store its centre its radius etc.

37
Q

What is a vector drawing list?

A

Properites which are stored in a list in order to redraw the vector

38
Q

Why might vector images be used instead of bitmaps?

A

Vector images will always be sharp regardless and the amount of data required to store the image will not change

39
Q

Advantages of vector graphics:

A

Typically smaller files sizes, no loss of quality, individual objects can be manipulated, if an objcet is deleted no hole will be left

40
Q

Advantages of bitmapped graphics:

A

Individual pixels can be manipulated within a bitmap image

41
Q

How is sound converted from analouge to digital format?

A

The ADC samples the analogue data at a given frequency and converts each amplitude into a binary value. In reverse a DAC is used

42
Q

What is the sampling rate

A

The frequency which you record the amplitude of the sound

43
Q

Why is a higher sample rate better?

A

High resolution

44
Q

How to calculate sample size?

A

number of samples per second x the number of bits per sample x the length of sample in seconds

45
Q

What is Nyquists Theorem?

A

You must sample a sound at a rate that is at least double the highest frequency component in the original sound

46
Q

What is MIDI?

A

Musical intrument digital interfice is a technical standard that describes a protocol digital interface and connecters which can be used to allow a wide variety of electronic music

47
Q

What does a MIDI controller do

A

It carries event messages

48
Q

What are event messages?

A

They are a sound processor that can be linked to several intruments of computers that specify pitch and duration of not, timbre, vibrato and volume changes and synchronzies temp between multiple devices

49
Q

What is a MIDI file?

A

It is a list of instructinos that tell it to synthesise a sound based on pre recoreded digital samples

50
Q

Why are MIDI files good?

A

Can use 1000 times less disk space than a conventional recordin gat an equivalent quality

computer science (8 decks)

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