Menu
I'm taking a quiz on an intro level class in C++ and I'm trying to understand a question. After searching the internet and not getting an answer, so here I am.
Which of the following function declarations will accept either cout or a file stream
object as its argument?
A. void output( fstream &outFile);
B. void output( ofstream &outFile);
C. void output( ostream &outFile);
D. void output( iostream &outFile);
The answer is C.
I know the difference between: fstream, ofstream, ostream, iostream.
What I don't understand is why none of the other options are able to accept the cout or file stream object as an argument.
Is the answer as simple as ostream objects contain data (char,etc) that are able to be passed as arguments?
Any information would be greatly appreciated.
976
ofstream is output file stream which allows you to write contents to a file. fstream allows both reading from and writing to files by default.
Dealing with files is similar to dealing with standard input and standard output; classes ifstream, ofstream, and fstream are derived from classes istream, ostream, and iostream, respectively.
The fstream term stands for File Stream. Stream refers to a sequence of characters moving from the disk to the C++ program or from the C+ program to the disk. Moving characters from a file in disk to the program is inputting. Moving characters from the program to a file in the disk is outputting.
The iostream: This class is responsible for handling both input and output stream as both istream class and ostream class is inherited into it. It provides function of both istream class and ostream class for handling chars, strings and objects such as get, getline, read, ignore, putback, put, write etc..
The answer is C. The question is about the inheritance hierarchy. std::cout is an instance of std::ostream. All other functions accept subclasses of std::ostream and can therefore not handle std::cout. std::fstream could be passed to all of them but the question was about both.
170
If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
Donate Us With
