Explain different types of file access method.

Different types of file access method:
There are three ways to access a file into a computer system: Sequential-Access, Direct Access,
Index sequential Method.
Sequential Access
• Data is accessed one record right after another record in an order.
• When we use read command, it move ahead pointer by one
• When we use write command, it will allocate memory and move the pointer to the end of
the file
• Such a method is reasonable for tape.
Direct Access
Another method is direct access method also known as relative access method. A filed-length
logical record that allows the program to read and write record rapidly. in no particular order. The
direct access is based on the disk model of a file since disk allows random access to any file block.
For direct access, the file is viewed as a numbered sequence of block or record.
Index sequential method
It is the other method of accessing a file which is built on the top of the direct access method.
These methods construct an index for the file. The index, like an index in the back of a book,
contains the pointer to the various blocks. To find a record in the file, we first search the index and
then by the help of pointer we access the file directly.