Chapter 4 - Representing Data Flashcards

1
Q
In binary what does 
1 + 0 =
1 + 1 =
0 + 0 =
1 + 1 + 1 =
A

1 + 0 = write 0 carry 1 over
1 + 1 = write 0 carry 1 over
0 + 0 = write 0
1 + 1 + 1 = write 1 carry 1 over

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2
Q

What is an overflow error?

A

When the result of an addition is too big to fit in the available space
Eg. When a computer uses storage values that are 8 bit long, by adding two 8 bits long numbers, the result may be bigger than 256 - you need a 9th binary digit, the 9th digit will be lost

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3
Q

Count to 15 in hexadecimal

A
0
1
2
3
4
5
6
7
8
9
A
B
C
D
E
F
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4
Q

Why use hexadecimal numbers?

A

Large binary numbers are hard to remember and programmers want something that is easily converted from binary an easy to remember and recognise

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5
Q

How are images stored?

A

Images are stored as a series of binary values, each binary value is one pixel

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6
Q

What is metadata and why is there a need for it?

A

Metadata is data about data
It includes height and width, resolution, but depth etc
There is a new for metadata because it enables the computer to work out how to turn these binary values into an image

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7
Q

What is height and width measured in?

A

Pixels

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8
Q

What is couloir depth?

A

The number of bits used per pixel, or how many colours each pixel can represent
1 bit = 2 colours black or white
2 bits = 2*2 colours or 4 colours
Etc.
The more bits per pixel the greater the colour depth

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9
Q

What is resolution?

A

Number of pixels per unit eg number of pixels per inch or dpi (dots per inch)

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10
Q

The higher the colour depth and the higher resolution, what happens to the size of an image file?

A

It increases

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11
Q

When does an image become pixelated?

A

When a bitmapped image is enlarged

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12
Q

What are the units of storage?

A
Bit 
Nibble
Byte
Kilobyte
Megabyte
Gigabyte
Terabyte
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13
Q

How are characters steed?

A

All characters and symbols are represented by a code
The codes used are stored in binary
The computer looks up the symbol matching the code from a list of codes and their associated character

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14
Q

What is a character set?

A

The list of codes and matching characters is called a character set

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15
Q

What determines how many symbols are in a character set?

A

The number of bits used to store each symbol

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16
Q

Examples of character sets?

A

Unicode

ASCII

17
Q

How many bits does ASCII use?

A

8 bits per character = 256 possibilities

18
Q

How many bits does uni code use?

A

16 bit providing 65 000 possibilities

Or 32 bits = 4 billion possibilities

19
Q

Why is unicode better than ascii?

A

Because it provides a wider range of characters and symbols facilitating communication

20
Q

What is sound and how is in stored in digital form?

A

Sound is analogue (continuously varying) so to transfer sound to a computer it must be digitally sampled.

21
Q

What is sample rate?

A

The number of samples in a second

22
Q

What is sample interval?

A

The time between samples been taken

23
Q

The higher the sample interval…

A

The lower the sample rate

24
Q

When a sound is sampled at a low rate:

A

Very few samples are taken
There is poor match between the original sound and the samples sound
A small file size is required

25
Q

When sound is samples at a high rate:

A

Many more samples are taken
There is a good match between the original sound and the sampled sound
A large file size is required

26
Q

What is bit rate?

A

The amount of storage space used for exam sample

27
Q

A high bite rate means:

A

More accurate sampling at each point which gives better quality
More data needs to be stored so larger file size

28
Q

What are the two parts of an instruction?

A

Operator: the instruction part eg. An operation
Operand: the data part, it is what the operator uses eg. A memory location

29
Q

How does a computer tell the difference between data and instructions?

A

It doesn’t, it simply deals with what it finds according to what it expects to find

30
Q

What is the accumulator?

A

A special register in the CPU used to store the results of any calculation