I'm stuck on a point while reading about these different accessing methods. As per author.
Memory is organized into units of data, called records.Access must be made in a specific linear sequence.
I understand that it will take variable time to access due to sequential ordering.
individual blocks or records have a unique address based on physical location.Access is accomplished by direct access to reach a general vicinity plus sequential searching,counting,or waiting to reach the final location. Again, access time is variable.
Here I'm Stuck that if we have unique address why it is taking variable time and why we can't directly access data.
Each addressable location in memory has a unique,physically wired-in addressing mechanism. The time to access a given location is independent of the sequence of prior accesses and is constant.
What is the difference between this and direct access method.