C++ Primer Plus

Random Access

For our last file example, let’s look at random access. Random access means moving directly to any location in the file instead of moving through it sequentially. The random access approach is often used with database files. A program will maintain a separate index file, giving the location of data in the main data file. Then it can jump directly to that location, read the data there, and perhaps modify it. This approach is done most simply if the file consists of a collection of equal-sized records. Each record represents a related collection of data. For example, in the example in Listing 17.19, each file record would represent all the data about a particular planet. A file record corresponds rather naturally to a program structure ...