Sequential access vs direct access vs random access in operating system

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Data is stored in the computer in many forms. One way of storing data in computers is in magnetic tapes also known as magnetic drives or hard drives. In hard drives data is kept for long period of time. We can store files, movies, songs, databases in hard drives which we need on daily basis. Some type of data that we don’t need is erased from the computer by us. But that deleted data still exists on hard drives and can be retrieved by different recovery software.

For accessing data faster, we use random access memory also known as RAM. Since RAM data is temporarily stored in random locations. Each location is given an ID to identify it. Data is stored in RAM in an index form like we store data in arrays. In indexing, each item is recognized by an item number also known as the index. For reading data from RAM, we use direct access method. As operating system knows all the indexes stored in the RAM, it can access data directly. Indirect memory access we need extra memory for storing index locations, header, footer etc.

Below is the diagram which illustrates how data is read in sequence.

Sequential access vs direct access in operating system
Sequential access vs direct access to operating system

Random access is also known as direct access.

Old windows operating systems use sequential programming in networks. Direct access to networks was first time introduced in windows server 2008, then in Windows 7 and Windows 8.

Old tape drives use sequential access while hard drives use direct access to read and write to files. In random access it may take longer time to read a large amount of data, the reason behind is that as data is stored in different random locations so hard drive head has to move to different locations many times.

In mobile networks we use direct access for faster connection between different devices and data is retrieved instantly.


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Junaid Rehman

I am a blogger and freelance web developer by profession. I love to blog and learn new things about programming and IT World.