secodary storage devices

Topics: Floppy disk, USB flash drive, Blu-ray Disc Pages: 3 (728 words) Published: May 3, 2014

Assignment 01
Information Systems Concepts
Dr.Yamaya Ekanayake

Access Methods of Secondary Storage Devices
Secondary Storage Device is storage medium which is used to store large amount of data permanently until it is changed by user. Though it stores information, it cannot be accessed directly by the CPU. The data stored in Secondary Storage Device can be accessed depending upon how it is stored on the device. Mainly there are two methods of accessing data from the Secondary Storage Device. 1) Sequential Access Method

2) Direct Access Method

Sequential Access Method – This means the computer system must search the storage device from the beginning until the desired data is found. The most common sequential access device is magnetic tape where data is stored and processed sequentially. For example, a tape contains information regarding students of a school, to look student’s number 100’s information, the computer will have to start with student number 1 and then go pass 2, 3, 4 and so on until it comes to 100. This method is quite simple than other methods, but it is very slow (more time for searching data) & very suitable for bills & payroll applications. Direct Access Method – This is also known as random access, it means the computer can go directly to the location where the data is stored that the user wants. The most common direct access devices are magnetic disc & optical disc. In these devices, the data is stored as sequentially numbered blocks. Thus one can access block 12, then block 78, then block 5 & so on. This method is ideal for applications like airline reservation system or computer –based directory assistance operations

Secondary Storage Device
Access Method
Magnetic tape
Sequential access
Access time is slower than hard drive
Magnetic Disk
Floppy disk
Direct access
Access time is very slow

Hard disk
Direct access
Access time is very fast ( currently the fastest)

Zip disk
Direct access...
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