Computing
How the machines and the protocols actually behave. 3 reviewed articles here, each naming the sources behind it.
What computing covers here
How the machines and the protocols actually behave. These are the questions a general reference work tends not to answer well — comparisons, causes, and the distinctions people routinely conflate.
Every one of these was read by a person
An article appears in this list only once somebody has checked it against its sources. Drafts and short articles are readable but are kept out of search and out of this list.
- How does a QR code still scan when part of it is damaged? — A QR code carries Reed–Solomon error correction, which stores mathematically redundant data so that up to 30% …
- Why do barcodes have a check digit? — The last digit of a barcode is computed from the others, so a scanner can immediately tell that it has misread…
- Why does Wi-Fi get slower when more devices join? — Because Wi-Fi is a shared medium in which only one device can transmit at a time on a channel — adding devices…
Questions
How does a QR code still scan when part of it is damaged?
A QR code carries Reed–Solomon error correction, which stores mathematically redundant data so that up to 30% of the symbol can be missing or wrong and the original message can still be reconstructed exactly.
Why do barcodes have a check digit?
The last digit of a barcode is computed from the others, so a scanner can immediately tell that it has misread something — a check digit does not correct errors, it detects them, and detecting a misread is the whole point at a till.
Why does Wi-Fi get slower when more devices join?
Because Wi-Fi is a shared medium in which only one device can transmit at a time on a channel — adding devices does not add capacity, it adds contention, and the time spent negotiating whose turn it is grows faster than the number of devices.