error checking and character sets Flashcards

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1
Q

what is a parity bit

A

an extra bit added to a string of binary code to ensure that the total number of 1-bits in the string is even or odd

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2
Q

how to get an even parity

A

If the data already has an even number of 1-bits, the parity bit is set to 0; if odd, the parity bit is set to 1

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3
Q

how to do an odd parity

A

Ensures the total number of 1-bits in the data is odd. If the data already has an odd number of 1-bits, the parity bit is set to 0; if even, the parity bit is set to 1

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4
Q

what would happen if one of the bits get corrupted using parity bit

A

the computer will change one of the bits, however it doesn’t know exactly which but has been corrupted

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5
Q

what is majority voting and wheres it used

A

an error detection and correction method where each bit of data is sent multiple times (usually three times). The receiver checks each set of bits and uses the value that appears most frequently.

  • used in space communication, critical financial transactions
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6
Q

What is a check digit and how is it used?

A
  • an additional digit added to a number (such as a barcode or bank account number) that is calculated from the other digits in the number.
  • It is used to detect errors in data entry or transmission.
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7
Q

Where would check digit be used in?

A

In applications, where therewill be manual input, which has high likelihood of human error

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8
Q

what are checksums

A
  • a mathematical algorithm applied to a block of data

— the data from the block is used in order to create the original checksum which is then added and transmitted along with the original data

— if the checksums match, the data has been transmitted correctly

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9
Q

how many combinations of 0s and 1s can a byte hold

A

256

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10
Q

how many bits are in a byte

A

8

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11
Q

what are character sets

A

a collection of characters used to represent text in a computer system

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12
Q

how to fix there not being enough characters

A

create a character set that is larger than 1 byte/8 bits

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13
Q

unicode character sets are at least how long

A

16 bits long, giving us an increase in combination of 0s and 1s

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14
Q

what is the job of the parity bitin odd or even parity

A
  • used to ensure that the total number of 1s in each byte, including the parity bit equals an odd or even number
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15
Q

what is overflow

A

where a carry from the most significant bit requires an additional bit

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16
Q

what is an unsigned representation

A

a binary representation that can only represent positive numbers

17
Q

what is signed representation

A

can represent both positive and negative numbers

18
Q

why was unicode introduced instead of ascii

A
  • to enable the representation of a greater range of characters
  • so that more languages can be represented
  • improved portability of documents
19
Q

advantages of using majority voting over parity bit

A
  • majority voting can identify and correct errors due to the majority bits being taken as the correct value
  • more effective at detecting errors, as parity bit may miss errors if an even number of bits are corrupted
  • can detect multiple errors as each triplet represents one bit of data and can identify tan error on that but
20
Q

explain how the even parity works using the roles of the sending and receiving device

A
  • sender counts the number of 1s in the bit pattern and adds an extra bit to ensure even number of 1s
  • receiver counts the number of 1s in the bit pattern received
  • if there are an odd number of 1s, it identifies that an error has occurred
21
Q

A data transmission system uses even parity.
Explain how the receiver will perform error detection on a received byte

A
  • If the number of 1s received/in the byte is even, the data is (assumed to have been)
    received correctly
  • If the number of 1s received/in the byte is odd, the data has been corrupted / is
    incorrect;
22
Q

what is a byte

A

a group of 8 bits

23
Q

how many values can be represented with n bits

A

2^n

24
Q

quantities of bytes (10^n)

A
  • kilo, k - 103
  • mega, M - 106
  • giga, G - 109
  • tera, T - 1012
25
Q

quantities of bytes (2^n)

A
  • kibi, Ki - 2^10
  • mebi, Mi - 2^20
  • gibi, Gi - 2^30
  • tebi, Ti - 2^40
26
Q

What is a character code

A

a binary representation of a character used by computers to store and manipulate text.

27
Q

What are the advantages and disadvantages of majority voting?

A

Advantages:

  • Can detect and correct errors, making it more reliable than simple error detection methods.
  • Effective in environments with high noise like telecommunications
  • Ensures high data integrity by using redundancy

DISADVANTAGES:
- Requires multiple transmissions of the same data, increasing bandwidth and storage requirements.

  • Latency: Increases latency in data transmission due to the additional data being sent and processed
28
Q

What are the advantages and disadvantages of parity bits?

A

Advantages:

Simplicity: Easy to implement and understand, requiring minimal additional resources.

Speed: Quick error detection method with minimal processing overhead.

Low Overhead: Adds only a single bit to each data unit, minimally increasing data size.

Disadvantages:

Limited Detection: Can only detect single-bit errors and fails with multiple bit errors.

No Correction: Capable only of error detection, not correction.

False Positives: May not detect some types of errors, leading to potential data integrity issues

29
Q

What are the advantages and disadvantages of check digits?

A

Advantages:

  • Easy to calculate and verify, requiring minimal computational resources.
  • Commonly used in applications such as barcodes, ISBNs, and account numbers.

Disadvantages:

  • Primarily used for numeric data, not effective for binary or alphanumeric data.
  • Can only detect errors, not correct them.
  • May not detect all types of errors, especially complex or multiple errors
30
Q

where is parity bit used

A

Internal computer memory, basic network communication

31
Q

disadvantages of unicode

A

each character will require more bits