We store any type of data in computer in files. Whether it is image, presentation, excel or any other form of data, it is stored in the form of files. There are two main methods of accessing the files from the computer. One method is known as sequential access and other is known as random access. Today I am going to discuss about sequential access. Sequential access is also known as serial access.
Sequential access is reading any file by searching from the storage device from the beginning. Let’s suppose that there are four files stored in the storage device. Now if you want to access 3rd file then you start searching the 3rd file from beginning of the storage device i.e. 1, 2, 3, 4. You have to go through 1 and 2 to access 3. Similarly if you open any file then data is also saved in file in sequential i.e. old data of the file is stored in old index and new data is stored in higher index. Now to access the data in the file computer has to access data from lower index to higher.
Let’s take an example of audio cassette that we have used in old days to listen the songs. Now there are songs stored in the cassette in sequence. To access song 4 we have to forward the cassette from song 1 to song 4 and similarly to listen to song 1 we have to do rewind the cassette. Same happen in magnetic tape used in computer. Files are stored in sequence in magnetic tapes and to access any file magnetic tape head has to move forward or backward in sequence. Another example of sequential access is video tape used VCR in old days. The same process happen in video tapes as in audio cassette.
Nowadays most of storage devices use random access instead of sequential access. Random access is reading any file directly without searching from beginning. For reading large amount of data, sequential access is preferred and fast method.