Week 3, 4 (Quiz 2) Flashcards
What is a data word?
The RAW data we want to protect, store, and send.
What is a code word?
The data word, but with extra bits.
What are the “extra bits” in a code word? What do they do?
These extra bits are called “parity bits”, “check bits”, and “redundant bits”.
They add overhead, but they help us to detect and fix errors.
What is overhead?
When we add extra bits to a data word, making it a code word.
What is a Hamming Code?
An error-correcting code use in computer science and telecommunication.
What is the Hamming Distance?
Measures the MINIMUM number of substitutions, or flips, required to change one valid code word into another valid code word.
How many errors can a Hamming code DETECT?
Code-length - 1.
Ex: in an 8-bit code, we can detect 7 errors.
How many errors can a Hamming code CORRECT?
(Code-length / 2) - 1
What is a HDD platter?
The circular disk on which magnetic data is stored in a hard drive.
What is a HDD track?
A track along which magnetic information is stored on a HDD. Tracks are located at certain radii.
What is a HDD sector?
A subdivision of a track; each sector holds a fixed amount of data.
In addition to data, sectors also contain a header, footer, gap, and info like error-correcting codes.
What is the order a HDD moves in to read/write info?
1) Move
2) Wait
3) Read
4) Write
What is a HDD cylinder?
Any set of ALL tracks of equal diameter on ALL platters.
What is seek time?
The time it takes for the read/write head to get to the desired TRACK.
What is rotational latency?
The time required to position a specific sector under a read/write head.
