Fundamentals of data representation

What is data?

Raw facts and figures without context

What is information?

Processed data that has meaning

What is a bit?

Smallest unit of data (binary digit: 0 or 1)

What is a byte?

8 bits

What is a nibble?

4 bits (half a byte)

What is a kilobyte (KB)?

1,024 bytes

What is a megabyte (MB)?

1,024 kilobytes

What is a gigabyte (GB)?

1,024 megabytes

What is a terabyte (TB)?

1,024 gigabytes

Why use 1024 instead of 1000?

Computers use binary (powers of 2: 2^10 = 1024)

What is binary?

Number system using only 0 and 1

What is denary?

Number system using 0-9 (decimal, base 10)

What is hexadecimal?

Number system using 0-9 and A-F (base 16)

Why do computers use binary?

Electronic circuits have two states: on (1) and off (0)

What is a binary digit called?

Bit

What does the rightmost bit represent in binary?

1 (2^0)

What is the place value of the second bit from right?

2 (2^1)

What is the place value of the third bit from right?

4 (2^2)

What is the place value of the fourth bit from right?

8 (2^3)

Convert binary 1011 to denary.

11 (8+0+2+1)

Convert binary 11111111 to denary.

255

Convert denary 13 to binary.

1101

Convert denary 255 to binary.

11111111

What is the largest number in 8 bits?

255

How many different values in 8 bits?

256 (0-255)

Formula for number of values with n bits?

2^n

How many values with 4 bits?

16 (2^4)

What is binary addition rule for 0+0?

0

What is binary addition rule for 0+1?

1

What is binary addition rule for 1+0?

1

What is binary addition rule for 1+1?

0, carry 1

What is binary addition rule for 1+1+1 (with carry)?

1, carry 1

What is overflow?

When result is too large for available bits

Example of overflow in 8-bit?

11111111 + 1 cannot be stored in 8 bits

What is a binary shift?

Moving bits left or right

What does left shift do?

Multiplies by 2 for each position

What does right shift do?

Divides by 2 for each position

What is 0101 shifted left once?

1010

What is 1000 shifted right once?

0100

What happens to bits shifted off the end?

They are lost

What is hexadecimal used for?

Shorter representation of binary, easier for humans

How many bits does one hex digit represent?

4 bits (one nibble)

What are hex digits 0-9?

Same as denary 0-9

What are hex digits A-F?

A=10, B=11, C=12, D=13, E=14, F=15

Convert hex F to denary.

15

Convert hex 1A to denary.

26 (1×16 + 10)

Convert denary 255 to hex.

FF

Convert binary 11111111 to hex.

FF

Why is hex useful for color codes?

Each color (RGB) uses 8 bits = 2 hex digits

Example of hex color code?

FF0000 (red)

What does #FFFFFF represent?

White

What does #000000 represent?

Black

What is a character?

Single letter, digit, or symbol

What is a character set?

Collection of characters a computer can represent

What is ASCII?

American Standard Code for Information Interchange

How many bits does ASCII use?

7 bits (extended ASCII uses 8)

How many characters in standard ASCII?

128

How many characters in extended ASCII?

256

What is Unicode?

Modern character set supporting all languages

How many bits does Unicode typically use?

16 or 32 bits

How many characters can Unicode represent?

Over 1 million

Why is Unicode better than ASCII?

Supports more languages, symbols, emojis

What is the ASCII code for 'A'?

65

What is the ASCII code for 'a'?

97

What is the ASCII code for '0'?

48

What is the ASCII code for space?

32

How are characters stored in computer?

As binary numbers using character set codes

What is an image made of?

Pixels (picture elements)

What is a pixel?

Smallest element of an image

What is resolution?

Number of pixels in an image (width × height)

What is color depth?

Number of bits used per pixel

What does 1-bit color depth give?

2 colors (black and white)

What does 8-bit color depth give?

256 colors

What does 24-bit color depth give?

16.7 million colors (true color)

How is 24-bit color depth split?

8 bits each for red, green, blue (RGB)

What is image file size formula?

Width × Height × Color depth

Calculate file size: 100×100 pixels, 24-bit color.

100 × 100 × 24 = 240,000 bits = 30,000 bytes = 29.3 KB

What is metadata?

Data about data

Examples of image metadata?

Width, height, color depth, date created

What is a bitmap image?

Image made of pixels

What happens when you enlarge bitmap?

Becomes pixelated (blocky)

What is image compression?

Reducing file size

What is lossy compression?

Compression that loses some data

Example of lossy format?

JPEG

What is lossless compression?

Compression without losing data

Example of lossless format?

PNG

When to use lossy compression?

Photos where small quality loss acceptable

When to use lossless compression?

Graphics, logos where quality critical

What is sound recorded as?

Analogue waves

What is sampling?

Taking measurements of sound wave at intervals

What is sample rate?

Number of samples per second

What is sample rate measured in?

Hertz (Hz)

What is CD quality sample rate?

44,100 Hz (44.1 kHz)

What is sample resolution/bit depth?

Number of bits per sample

What is CD quality bit depth?

16 bits

What is sound file size formula?

Sample rate × bit depth × duration × channels

Calculate: 1 second, 44.1kHz, 16-bit, mono.

44,100 × 16 × 1 = 705,600 bits = 88,200 bytes ≈ 86 KB

What are channels in audio?

Mono (1) or stereo (2)

How does higher sample rate affect quality?

Better quality, more detail

How does higher sample rate affect file size?

Larger file size