Checking state flags The following member functions exist to check for specific states of a stream all of them return a bool value:
Increase type safety, reduce errors, allow extensibility, and provide inheritability. Removing redundancy removes a class of errors. This means you can have other user-defined things that look and act like streams, yet that do whatever strange and wonderful things you want.
Why does my program go into an infinite loop when someone enters an invalid input character? For example, suppose you have the following code that reads integers from std:: In other words, the program enters an infinite loop; if 42 was the last number that was successfully read, the program will print the message You entered 42 over and over.
An easy way to check for invalid input is to move the input request from the body of the while loop into the control-expression of the while loop.
Naturally you can eliminate the break by changing the while loop expression from while std:: How can I get std:: For example, if you wanted the age to be between 1 andyou could change the while loop to: How old are you? Next the compiler notices that the returned std:: To convert an std:: So in this case the compiler generates a call to std:: For example, if you read one too many times e.
This expression returns std:: The next expression also returns a reference to std:: Because the eof state may not get set until after a read is attempted past the end of file.
That is, reading the last byte from a file might not set the eof state. For example, the following code might have an off-by-one error with the count i: Because the numerical extractor leaves non-digits behind in the input buffer.
If your code looks like this: Should I end my output lines with std:: This is so the output operations can be cascaded. These beliefs are naive and wrong: This is not to say that the printOn method approach is never useful. For example, it is useful when providing printing for an entire hierarchy of classes.
But if you use a printOn method, it should normally be protected, not public. The member-called-by-top-level-function approach has zero benefit in terms of maintenance cost. Thus moving the code from a friend function into a member function does not reduce the maintenance cost at all.
No benefit in maintenance cost.
The member-called-by-top-level-function approach makes the class harder to use, particularly by programmers who are not also class designers. The approach exposes a public method that programmers are not supposed to call. Therefore it is, in general, a bad idea. There are cases when that approach is reasonable, such as when providing printing for an entire hierarchy of classes.
How can I provide input for my class Fred? How can I provide printing for an entire hierarchy of classes? This is called the Virtual Friend Function Idiom. Note that derived classes override printOn std:: As to whether Base::Input/output via and Why should I use instead of the traditional?.
Increase type safety, reduce errors, allow extensibility. Input/output with files C++ provides the following classes to perform output and input of characters to/from files: ofstream: Stream class to write on files; ifstream: Stream class to read from files; fstream: Stream class to both read and write from/to files.; These classes are derived directly or indirectly from the classes istream and leslutinsduphoenix.com have already used objects whose types were.
HTTP Input and Output. HTTP input/output character encoding conversion may convert binary data also. Users are supposed to control character encoding conversion if binary data is used for HTTP input/output.
On a UNIX system, when an application reads from a file it gets exactly what's in the file on disk and the converse is true for writing.
The situation is different in the DOS/Windows world where a file can be opened in one of two modes, binary or text.
A computer punched card reader or just computer card reader is a computer input device used to read computer programs in either source or executable form and data from punched cards.A computer card punch is a computer output device that punches holes in cards. Sometimes computer punch card readers were combined with computer card punches and, later, other devices to form multifunction .
Input and Output Devices: Links to topics on this page: Before a computer can process your data, you need some method to input the data into the machine. The device you use will depend on what form this data takes (be it text, sound, artwork, etc.).