Data File - Opening and Closing Files in C++

Opening and Closing Files in C++

In C++, opening of files can be achieved in two ways:

1. Using the constructor function of the stream class.
2. Using the function open.

The first method is preferred when a single file is used with a stream, however, for managing multiple files with the same stream, the second method is preferred.

• Opening files using Constructors

ifstream input_file("DataFile");

The data being read from DataFile has been channelised through the input stream as shown:

The above given statement creates an object (input_file) of input file stream. The object name is a user defined name. After creating the ifstream object input_file, the file DataFile is opened and attached to the input stream input_file. Now both, the data being read from DataFile has been channelised through the input stream object. The connections with a file are closed automatically when the input and output stream objects expire i.e., when they go out of scope. (For instance, a global object expires when the program terminates). Also you can close a connection with a file explicitly by using close method

input_file.close;

Closing such a connection does not eliminate the stream, it just disconnects it from the file. The stream still remains there. Closing a file flushes the buffer which means the data remaining in the buffer (input or output stream) is moved out of it in the direction it is ought to be.

• Opening files using open function

ifstream filin; //create an input stream filin.open("Master.dat"); //associate '''filin''' stream with file Master.dat . //process Master.dat . filin.close; //terminate association with Master.dat filin.open("Tran.dat"); //associate '''filin''' stream with file Tran.dat . //process Tran.dat . filin.close; //terminate association

A stream can be connected to only one file at a time.