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Data Files and Streams

In the real world, computer applications need to store large amounts of data for extended periods of time.  Imagine the amount of data stored and accessed by the IRS.

  To accomplish the task of storing large amounts of data,
data files are used.

There are two types of data files:

Sequential Access Files:  These files must be accessed in the same order in which they were written.  This process is analogous to audio cassette tapes where you must fast forward or rewind through the songs sequentially to get to a specific song.  In order to access data from a sequential file, you must start at the beginning of the file and search through the entire file for the data that you want.

Random Access Files:  These files are analogous to audio compact disks where you can easily access any song, regardless of the order in which the songs were recorded.  Random access files allow instant access to any data in the file.  Unfortunately, random access files often occupy more disk space than sequential access files.


File Streams:

Remember that a C++ program views input (or output) as a stream of bytes.  On input, a program extracts (>>) bytes from an input stream.  On output, a program inserts (<<) bytes into the output stream.  The stream acts as a mediator between the program and the stream's source or destination.

In this same manner, input and output data is handled by use of a

 A buffer is a block of memory used as an intermediate, temporary storage area for the transfer of information between a program and a device (e.g. file).