What Is the Difference Between Sequential and Random Access?

According to computer memory manufacturer SanDisk, random access memory is distinguished from sequential memory by its ability to return any item stored in memory at any time without regard for the order in which items are stored. In contrast, sequential memory is only capable of accessing items in the order in which they are stored in memory.

SanDisk states that the primary advantage of random access memory is that it allows any element within a memory structure to be accessed in approximately equal time. Sequential access memory requires that any memory access begins at the first element in the memory structure, meaning that elements near the end of the sequential memory structure require more time to access than elements near the beginning. The differences between DVDs and videotapes provide an intuitive example of this concept; while DVDs permit random access to any scene in a film on demand, it is not possible to view a later scene on a video tape without viewing or fast-forwarding through the preceding scenes.

Sequential memory is more efficient than random access memory in some scenarios, however. As an example, SanDisk states that accessing data stored on a hard disk in a random access memory structure is less efficient than accessing the same data stored in a sequential access structure, as random access requires more time-intensive seek operations to locate the data. According to Wikipedia, sequential access memory storage devices are frequently less expensive and store more data than similarly priced random access devices. In addition, sequential access memory devices are often more durable than random access memory devices.