Basic Input Output in C - JohnHau/mis GitHub Wiki

In the above program, the insertion operator(<<) inserts the value of the string variable sample followed by the string “A computer science portal for geeks” in the standard output stream cout which is then displayed on the screen.

standard input stream (cin): Usually the input device in a computer is the keyboard. C++ cin statement is the instance of the class istream and is used to read input from the standard input device which is usually a keyboard. The extraction operator(>>) is used along with the object cin for reading inputs. The extraction operator extracts the data from the object cin which is entered using the keyboard.

The above program asks the user to input the age. The object cin is connected to the input device. The age entered by the user is extracted from cin using the extraction operator(>>) and the extracted data is then stored in the variable age present on the right side of the extraction operator.

Un-buffered standard error stream (cerr): The C++ cerr is the standard error stream that is used to output the errors. This is also an instance of the ostream class. As cerr in C++ is un-buffered so it is used when one needs to display the error message immediately. It does not have any buffer to store the error message and display it later. The main difference between cerr and cout comes when you would like to redirect output using “cout” that gets redirected to file if you use “cerr” the error doesn’t get stored in file.(This is what un-buffered means ..It cant store the message)