Question

Which code fragment correctly reads an int from standard input and writes twice its value to standard output?

A) `int num; cin >> num; cout << num 2;`
B) `cout << 2 cin >> num;`
C) `int num; cin << num; cout << num + num;`
D) `cout << cin 2;`

Answer 1

The correct code to read an int and output twice its value would involve declaring an int variable num, reading the value using cin, and outputting twice its value using cout. None of the choices provided are correct, but the example given shows how it should be done in C++ with the use of std cin and std cout.

Step-by-step explanation:

The question is asking which code fragment can read an integer from the standard input and output twice its value correctly. The correct option is not listed in the provided choices. However, a correct code fragment in the C++ programming language should look something like this:

int num; cin << num; cout << num + num;

This code declares an integer variable num, then uses the extraction operator (>>) to read a value into num from standard input (usually the keyboard). Finally, it uses the insertion operator (<<) to output twice the value of num to the standard output (usually the screen). Note that using the namespace std is a common practice when working with the C++ Standard Library.