IO - Random and Sequential Access

> I/O - (Input/Output|Read/Write) - Data Access

1 - About

Random access (sometimes called direct access) is the ability to access an arbitrary element of a sequence in equal time.

Random definition: can be accessed in any order

Random refers to the idea that any piece of data can be returned in a constant time, regardless of its physical location and whether or not it is related to the previous piece of data.

The opposite is sequential access, where a remote element takes longer time to access.

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3 - Example

3.1 - Device

Computer - Storage Device (Media)

Be careful as accessing media randomly as opposed to sequentially, typically yields minimum throughput.

3.1.1 - random access device

A compact disc: You can jump right to the track you want.

3.1.2 - sequential access device

a cassette tape, magnetic discs and optical discs

By contrast, storage devices such as magnetic discs and optical discs rely on the physical movement of the recording medium or a reading head. In these devices, the movement takes longer than data transfer, and the retrieval time varies based on the physical location of the next item.

With a cassette tape, you have to fast-forward through earlier songs to get to later ones. This type storage devices rely on the physical movement of the recording medium or a reading head. The movement takes longer than data transfer, and the retrieval time varies based on the physical location of the next item.

4 - Documentation / Reference

io/random_access.txt · Last modified: 2018/12/13 09:34 by 141.101.69.13