The terms random access and sequential access are often used to describe data files. A random-access data file enables you to read or write information anywhere in the file. In a sequential-access file, you can only read and write information sequentially, starting from the beginning of the file.

Both types of files have advantages and disadvantages. If you are always accessing information in the same order, a sequential-access file is faster. If you tend to access information randomly, random access is better.

Random access is sometimes called direct access.

True random access - article
Contains an overview of true random access as it pertains to the recording of television pictures.