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Computer Science > Unit 2 - Data Representation > Flashcards

Unit 2 - Data Representation Flashcards

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1
Q

What is the binary number system?

A

Computers use a binary number system consisting of only 0s and 1s. Everything a computer needs to process must be converted to a binary format.

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2
Q

What is the order of file size from smallest to biggest?

A

Bit (b)
Byte (B)
Kilobyte (KB)
Megabyte (MB)
Gigabyte (GB)
Terabyte (TB)
Petabyte (PB)

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3
Q

How much is is a bit?

A

A single 0 or 1.

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4
Q

How much is a nibble?

A

4 bits

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5
Q

How much is a byte?

A

8 bits - one character of text

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6
Q

How much is a Kilobyte?

A

1000 bytes

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7
Q

How much is a Megabyte?

A

1000 KB

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8
Q

How much is a gigabyte?

A

1000 MB

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9
Q

How much is a terabyte?

A

1000 GB

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10
Q

How much is a petabyte?

A

1000 TB

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11
Q

What is denary?

A

It is a base 10 number system with 10 digits 0-9

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12
Q

What is an overflow?

A

The generation of a number that is too large to be represented by the device intended to store it.

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13
Q

What is hexadecimal (or hex)?

A

A numerical system of notation that uses 16 rather than 10 as its base. The 16 hex base digits are 0 – 9 and the letters A – F.

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14
Q

How would you convert hex to denary?

A

Multiply the left side by 16 and add the units.
For example 2D: 2*16 = 32…………..32 + D(13) = 45

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15
Q

What are binary shifts?

A

Allows you to easily multiply or divide a base-2 binary number. A left shift multiplies the number by 2, while a right shift divides it by 2.

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15
Q

Why use hex?

A

It’s much simpler to remember hex than binary. It is quicker to write, less likely to make an error, and easy to convert.

15
Q

How would you convert denary to hex?

A

Divide the denary by 16. This would give the left-hand hex digit. The remainder would be the units.

16
Q

What is ASCII?

A

ASCII (American standardised code for information interchange) is a character set devised for early telecommunication systems but proved to be ideal for computer systems. Uses 7 bits, providing 32 control codes and 96 displayable characters. The eighth bit is often used for error checking.

17
Q

What is Unicode?

A

Standard character set that replaces the use of multiple different character sets. Incorporates characters from almost all global languages. A 16-bit extension of ASCII.”

18
Q

What are the 5 different image file formats?

A

. BMP - Bitmap
. JPG -
. TIFF
. PNG
. GIF

19
Q

What are pixels?

A

“The smallest unit of a digital image or graphic that can be displayed on a digital device. A pixel is represented by a dot or square on a computer display. Each pixel would have a colour represented by a binary number. The colour can change by changing the binary number.

20
Q

What is colour depth?

A

Colour depth, or bit depth, is the number of bits used for each pixel.
1 bit per pixel = 2¹ = 2 colours
2 bit per pixel = 2² = 4 colours
3 bit per pixel = 2³ = 8 colours
A higher bit depth gives us a greater range of colour and a better quality image.

20
Q

What is resolution?

A

Resolution is the concentration of pixels within a specific area. The area is defined by the image width and height in pixels.

21
Q

How would you calculate image file size?

A

The total size of an image file in storage. Size in bits = Width in pixels * Height in pixels * Colour depth in bits.

22
Q

What is metadata?

A

metadata is a collection of data that provides info about other data. This would include:
. Bit depth in bits per pixel
. Resolution
. Data created
. Author

23
Q

What is a bitmap graphic made up of?

A

It is made up of individual pixels.

24
Q

How must sounds be converted to so that it can be stored by a computer?

A

It must be converted from analogue to digital.

25
Q

What is sample rate?

A

The number of samples taken per second.

26
Q

What is sampling?

A

Sampling is the process whereby an analogue wave is converted into a digital signal.

27
Q

What is sample duration?

A

How many seconds of audio a sound file contains.

28
Q

What is image quality?

A

The overall detail of an image, affected by colour depth and resolution.

29
Q

What are samples measured in?

A

Hertz (Hz)
1 Hz = 1 sample per second

30
Q

What is sample resolution?

A

The number of bits used to record each measurement. More bits per sample enables the height of the wave to be more accurately measured, but this increases the file size.

31
Q

What is the formula to calculate sound file sizes?

A

File size (bits) = sample rate * resolution * seconds

32
Q

How does recording quality improve?

A

. The more frequently we sample the sound
. The more accurately we record the wave height.

33
Q

What is lossy compression?

A

A compression method that generally involves a loss of quality where experience tells us that it will be least noticed. It permanently deletes part of the data and tries and reconstruct the file.

34
Q

What is lossless compression?

A

A compression method that allows a file to be recreated in its original quality. It leaves out repeated data and makes a note of how many times it is repeated.

35
Q

What are the benefits of compression?

A

. Download times are reduced
. Voice can be transmitted fast enough to keep up with speech.
. Reduces traffic over the internet
. Quicker to complete transmission

36
Q

What is buffering?

A

This is caused when the download speed is slower than the playback speed.

Computer Science (6 decks)

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