← Error Detection (Parity Magic Trick)
Flashcards
Error Detection (Parity Magic Trick)
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Error Detection (Parity Magic Trick) — Flashcards
| Front | Back |
|---|---|
| What is error detection? | Recognizing when data has been corrupted (changed accidentally). |
| What is error correction? | Being able to reconstruct the original, correct data after an error is found. |
| What is a "parity card" (or parity bit)? | An extra card/bit added to a row or column to make the number of coloured cards (or 1s) even, used to detect errors. |
| In the Card Flip Magic trick, how many cards are laid out initially? | 36 cards in a 5×5 square, plus an extra row and column added by the magician. |
| How does the magician choose the "extra" cards in the demonstration? | So that every row and column has an even number of coloured cards showing. |
| How does flipping one card reveal itself in the trick? | The row and column containing the flipped card will each have an odd number of coloured cards, pinpointing the error. |
| What does "even parity" mean? | Using an even number of coloured cards (or 1s) in each row/column as the check condition. |
| What is remembered about the number 0 in parity counting? | Zero is considered an even number. |
| What happens if two cards are flipped instead of one? | It is not always possible to tell exactly which two cards changed, but it can be detected that an error occurred; it can usually be narrowed to one of two pairs. |
| What happens if four cards are flipped? | It is possible that all parity checks still come out correct, so the error could go undetected. |
| What is special about the lower right-hand "corner" parity card? | If chosen correctly for its column, it will also always be correct for its row (with even parity). |
| Can odd parity be used instead of even parity? | Yes, but the corner card only works for both row and column if the number of rows and columns are both even or both odd. |
| What is an ISBN? | International Standard Book Number — a ten-digit code found on published books, with the tenth digit as a check digit. |
| How is an ISBN checksum calculated? | Multiply digits 1–9 by 10 down to 2 respectively, add the results, divide by 11, and subtract the remainder from 11 (unless remainder is 0) to get the check digit. |
| What does the letter "X" represent in an ISBN checksum? | It represents a checksum value of 10, since a single digit can't show two digits. |
| Name common errors found in ISBN or barcode numbers. | A digit's value is changed, two adjacent digits are swapped, a digit is inserted, or a digit is removed. |
| Why is error detection important for transmitted data (e.g., bank deposits)? | Because interference during transmission could accidentally change important data, such as turning $10 into $1,000. |
| Why can't errors always simply be corrected by resending data? | Because retransmission may be impractical, e.g., data from a deep space probe (over half an hour delay from Jupiter) or damage to a disk/tape. |
| How do computers use parity for error detection and correction? | By arranging bits into imaginary rows and columns and adding parity bits to each, allowing detection and correction of the exact bit that changed. |
| What is the joke referenced at the end of the resource? | "Pieces of nine, pieces of nine" is called a "parroty error" — a play on "parity error." |
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