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Introduction to Computer Science > Chapter 4 (Pt. 2) > Flashcards

Chapter 4 (Pt. 2) Flashcards

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1
Q

How does black/white encoding differ from RGB?

A

Each pixel is encoded with either 0 (white) or 1 (black).

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2
Q

How is the greyscale encoded?

A
  • 8 bits can be used to represent 256 different shades of gray
  • 0 (black) to 255 (white)
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3
Q

How are color images encoded?

A

16 colors (4 bits per pexl)… use a color palette

256 colors (8 bits per pixel)

RGB True Color (Red Value, Green Value, Blue Value)

  • Typically 8 bits per color (total of 24 bits per pixel)
  • 16.7 million different colors.
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4
Q

Define:

Vector Graphics

A

All components of the image are stored

Can be easily scaled without losing image quality

Common Vector Formats

  • Adobe Illustrator
  • CorelDRAW
  • MathML
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5
Q

Define:

Data Compression Algorithms

A

Attempt to represent information in ways that preserve accuracy while using significanlty less space.

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6
Q

Define:

Compression Ratio

A

Measures how much compression schemes reduce storage requirements of data.

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7
Q

Define:

Run-length Encoding

A

Replaces a sequence of identical v1, v2,…,vn by a pair of values (v, n).

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8
Q

Define:

Variable Length Code Sets

A
  • Often used to compress text
    • More efficient
  • Can also be used with other forms of data.
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9
Q

Define:

Lossless Compression Schemes

A
  • No information is lost in the compression
  • It is possible to exactly reproduce the original data.
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10
Q

Define:

Lossy Compression Schemes

A
  • Do not gaurantee that all of the information in the original data can be fully and completely recreated
  • Trade image quality for file size
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11
Q

Which are the common Raster Image File Formats?

A

JPEG (Joint Photographic Experts Group)

  • 8 bit grayscale, 24 bit color
  • Compression is lossy

TIFF (Tagged Image File Format)

  • 8 bit or 16 bits per color
  • Compression can be lossy or lossless

GIF (Graphics Interchange Format)

  • 8 bit color palette
  • LZW lossless compression
  • Is now patent-free

BMP

  • Uncompressed, large, lossless, simple structure

PNG (Portable Network Graphics)

  • Free open-source alternative to GIF
  • 8 bit color palette, 24-bit truecolor, 48-bit true color
  • Compression is lossless
  • Patent-free replacement for GIF
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12
Q

Why is binary representation reliable?

A

Computers use binary representation for reasons of reliability.

Building a base-10 “decimal computer”

  • Requires finding a device with 10 distinct and stable energy states that can be used to represent the 10 unique digits (0,1,….,9) of the decimal system.

Bistable Environment

  • Only two (rather than 10) stable states separated by a huge energy barrier.
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13
Q

What is the universal storage medium?

A
  • No practical universal storage medium exists
  • All forms of storage have drawbacks
  • Computer systems contain several kinds of storage
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14
Q

Describe the storage hierarchy.

A

Primary

  • Directly accesible to the CPU
  • Relatively expensive
  • RAM (volatile) … access time in nanoseconds
  • ROM (non-volatile)
    • Contains a small startup program (BIOS)
    • Reads a larger program from non-volatile secondary storage to RAM and start to execute it.

Secondary

  • Not direclty acessible by the CPU
  • Relatively cheap
  • Non-volatile
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15
Q

What are the types of secondary storage mediums?

A

Hard disk drives … access time in milliseconds

Rotating optical storage devices

  • Longer access times than hard disk drives
  • CD drive
  • DVD drive

Flash Memory

  • USB Flash drives
  • SD cards
  • Memory Stick (Sony)

Solid State Drives

Hybrid Drives

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16
Q

Describe virtual memory

A
  • As primary memory fills up, the least-used data is moved to secondary storage devices (swap file)
  • This data is retrieved when needed
  • More retreivals mean overall system performance is degraded
17
Q

Describe offline storage

A
  • Storage that can be physically removed or disconnected
  • Inreases general information security
  • Useful for archiving data
18
Q

What are the seven characteristics of storage?

A
  • Volatility
  • Mutability
  • Accessibility
  • Addressability
  • Capacity
  • Performance
  • Energy Use
19
Q

Define:

Non-volatile Memory

A
  • Retain stored information without power
  • Suitable for long-term storage
20
Q

Define:

Volatile Memory

A

Requires constant power to maintain stored information

Types

  • Dynamic Random-Access Memory (DRAM): requires stored information to be preriodically re-read and re-written (refresh) or it will be lost
  • Static Random-Access Memory (SRAM): does not need to be refreshed as long as power is applied.
21
Q

Define:

Mutable Storage

A

Read/Write Storage

  • Allows information to be overwritten at any time
  • Example: RAM, hard disk drives
22
Q

Define:

Immutable Storage

A

Read Only Storage

  • Retains information stored at the time of manufacture

Write Once Storage

  • Allows information to be written only once at some point after manufacture
  • Example: CD-R
23
Q

Define:

Slow Write, Fast Read Storage (Mutability)

A

Allows information to be overwritten multiple times, but with the write operation being much slower than the read operation.

  • Example: CD-RW and Flash Memory
24
Q

Define:

Random Access

A
  • Any location in storage can be accessed at any moment in approximately the same amount of time
  • Most semiconductor memories and disk drives provide random access.
25
Q

Define:

Sequential Access

A

Accessing pieces of information is in a serial order, one after the other

The time to access a particular piece of information depends on which piece of information was last accessed.

  • Example: some off-line storage methods.
26
Q

Define:

Location-Addressable

A
  • Each individually accessible unit of information in storage is selected with its numerical memory address
  • Primary storage
  • Efficient
27
Q

Define:

File Addressable

A
  • Information is divided into files of variable length
  • Files are selected with directory and file names
  • Secondary, tertiary and off line storage
28
Q

Define:

Capacity

A

The total amount of stored information that a storage device can hold

Expressed as a quantity of bits or bytes

  • Megabyte
  • Gigabyte
  • Terabyte
  • Petabyte
29
Q

Define:

Latency

A
  • The time it takes to access a particular location in storage
  • Primary storage: expressed in nanosecond
  • Secondary storage: expressed in milliseconds
30
Q

Define:

Throughput

A
  • The rate at which information can be read from or written to storage
  • Expressed in megabytes per second, or MB/s
31
Q

What are some factors that affect energy use?

A

Factors

  • Fan usage (heat)
  • Shut down during inactivity
  • Power to operate

Types of devices

  • Hard disk drives (6 W at peak load)
  • Solid State Drives (2 W at peak load)
  • Hybrid drives
32
Q

Compare HDD versus SSD

A
33
Q

What is the construction of computer circuits based on?

A

Bolean Logic

34
Q

Define:

Bolean Expression

A

Any expression that evaluates to either true or false

35
Q

Define:

Truth Table

A

Can express the idea that the AND operation produces the value if and only if both of its components are true.

36
Q

Describe the Operators

A

AND: &

OR: |

XOR: ^

Introduction to Computer Science (6 decks)

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