Talk:Random access

Found a joke (i think)

A totally unrelated concept is universal access.

lol --BlckKnght

No it's wrong!

Random access is the ability to access a random element of a group in equal time.

No, the equal time might (or might not) be a consequence of random access but it not the defining property.

The opposite is sequential access

Not the opposite but an example of another access method.

The term random access memory (RAM), however, is used for ferrite core or semiconductor chip memory circuits used in computers.

No, random access is a property of the memory that does not depend necessarily on the technology used to implement it. It is possible to design ferite core memory etc where random access is not possible. The term random access memory is used for memory which can be accessed randomly. — Preceding unsigned comment added by Psb777 (talk • contribs) 11:23, 24 January 2004 (UTC)

I kind of think "random" is a misnomer, but a name that someone gave the technology in its infancy and it stuck. The word implies a probability distribution or lack of determinism, a concept which is unrelated to the concept of "random access".

Because of this I am changing the first line of this article from "random access is the ability to access a random element of a group in equal time" to "random access is the ability to access an arbitrary element of a group in equal time".

I believe in the existing sentence the word "random" was used improperly. The word "random" in random access is simply a name that the technology is called. But its actual function has little to do with randomness and so the word "random" should not be used in a description of the technology's function.

This is my opinion. If I am wrong, feel free to revert.

Mbarbier 21:51, 11 October 2006 (UTC)

I would guess its called random because no sequence of reads can be faster than a random sequence of the same length. --Tgr (talk) 20:26, 11 July 2008 (UTC)

Maybe say "sequential" is complementary to random (direct) access. Yes it is another access method, but in the usual systems those are the two choices.

Yes, direct access is a better description than random access. But both have the idea that you can get to an item without reading through all those in between. Gah4 (talk) 02:00, 17 February 2015 (UTC)

Removed deques

Deques are bad example for constant access time as they have linear O(n) access time. Removing. 71.59.115.159 (talk) 19:38, 28 December 2007 (UTC)

Most likely deques were added here because they have an implementation in C++ based on circular dynamic arrays that does allow random access. That's not usually part of the deque abstract data type though, so I agree with your edit. Dcoetzee 22:42, 28 December 2007 (UTC)

Compact disk

A compact disk (floppy disk, hard disk etc.) is not a good example for random access, as moving the head between tracks takes a lot more time than reading from a track. (Defragmenting would not speed up a truly random access device.) Neither is a book, which is literally random: you can't control exactly which page you open it at. I can't think of any good example except RAM and arrays. --Tgr (talk) 20:12, 11 July 2008 (UTC)

The book example is pretty much spot on. Assuming you know exactly where the page is located, you can open the book on it without going through any other pages. With a scroll, even if you know exactly where the data you're looking for is located you must go through any data segments in-between.

Though an alternative to the book vs scroll is to have open scroll vs rolled scroll. If you have a fully opened scroll, and you know exactly where the data is, you can literally point to it and say "Here it is". With a closed scroll you would need to roll/unroll to get to it. 71.203.81.151 (talk) 01:55, 6 April 2010 (UTC)

Might be good to give an explanation of how Ram and Arrays achieve this constant time look-up. Is it because they use goto? If so how does goto get around having to walk down each memory address to get to the data? Isn't this just a faster version of the Scroll example?

Magnetic disks are considered direct access, as opposed to sequential access for tapes. On most, it does take a little while longer to get to a farther away track, but usually much less than proportional to the distance. People are (or used to be) used to sequential access audio tape and direct access CDs, so I think the analogy is good, though as with most, not perfect. Gah4 (talk) 02:04, 17 February 2015 (UTC)

Quicksort

While randomized quicksort indeed needs random access to pick the pivot element randomly, the partition algorithm itself does not. I therefore replaced the reference with integer sorting where direct access is essential. WillNess (talk) 12:53, 21 September 2011 (UTC)

RFC: Hyphenate "random access" when used as compound modifier?

Should "random access" be hyphenated when used as compound modifier (e.g. Random-access memory)? Jojalozzo 02:23, 14 September 2012 (UTC)

Survey

• It depends. Follow standard English grammar, which depends on whether the compound is used as an adjective or not. Dicklyon (talk) 03:02, 14 September 2012 (UTC)

You are correct, I have modified my question to address this point. Thank you. Jojalozzo 03:08, 14 September 2012 (UTC)

So are you proposing that we not follow standard English grammar? I think it's WP style to not drop the hyphen, particularly to help the novice reader parse unfamiliar phrases. Dicklyon (talk) 03:12, 14 September 2012 (UTC)

Discussion

A discussion on renaming Parallel Random Access Machine prompted this question. I don't have a strong opinion but I think our usage should be consistent across the project. I see it unhyphenated more often than hyphenated, especially in titles, but it would be easy to change if we want to. Jojalozzo 02:29, 14 September 2012 (UTC)

The question here is malformed. In English, compound nouns get hyphens when used as modifiers, and not otherwise. It is common to drop the hyphen in compound modifiers when writing for an audience that is expected to be very familiar with a term and hence have no trouble with the ambiguous parse. When writing for a general audience, dropping the hyphen, adding to the ambiguity, is a bad idea, even if it is common. Dicklyon (talk) 03:02, 14 September 2012 (UTC)

Yes, my mistake. Thank you for the correction. Jojalozzo 03:08, 14 September 2012 (UTC)

Agreeing with people is not my strong point, but I agree with Dicklyon. For one thing his/her remark gells with my own experience and my own usage over a considerable period in this specific connection. JonRichfield (talk) 08:39, 18 September 2012 (UTC)

(Responding to the RfC). Moreover, Dickylon's advice accords with the Manual of Style. I can't see any good reason to ignore it in this instance. (See also the hyphen article). Anaxial (talk) 05:49, 25 September 2012 (UTC)