C++ for Python Programmers The PreTeXt Edition

Having created a stream with the declaration above, we can connect it to a file (i.e. open the file) using the member function open(filename). For example, the following statement will allow the C++ program to open the file called “myFile.txt”, assuming a file named that exists in the current directory, and connect in_stream to the beginning of the file:

in_stream.open("myFile.txt");

Once connected, the program can read from that file. Pictorially, this is what happens:

the <ofstream> class also has an open(filename) member function, but it is defined differently. Consider the following statement:

out_stream.open("anotherFile.txt");

Pictorally, we get a stream of data flowing out of the program:

Because out_stream is an object of type <ofstream>, connecting it to the file named “anotherFile.txt” will create that file if it does not exist. If the file “anotherFile.txt” already exists, it will be wiped and replaced with whatever is fed into the output stream.

To disconnect the ifstream in_stream from whatever file it opened, we use its close() member function:

in_stream.close();

To close the file for out_stream, we use its close() function, which also adds an end-of-file marker to indicate where the end of the file is:

out_stream.close();

Answer the question below concerning the use of the fstream library: