How many times 'save trees' will be displayed by C++ loop?
do { cout

Question

How many times 'save trees' will be displayed by C++ loop? 
do { cout << "save trees"; } while(0);

Accepted Answer

The correct option is (1):
The C++ code provided uses a do-while loop, a control flow statement characterized by its 'post-test' structure. This means the block of code inside the 'do' section is guaranteed to execute at least one time before the loop's condition, specified in the 'while' parenthesis, is ever evaluated. In this specific code, the statement `cout << "save trees";` runs first, immediately displaying the message 'save trees' once. After this execution, the program encounters the condition `while(0)`. In C and C++, the integer value 0 is logically interpreted as false, and since the condition is evaluated to false, the loop terminates without running for a second time. Therefore, the message is displayed exactly one time.

The incorrect option is (2):
The output will not be displayed two times. The `do-while` loop's body is executed only once because the termination condition is met immediately following the first iteration. The execution flow is not structured to re-enter the loop. If the `while` condition had been non-zero (like `while(1)` or a true expression) *and* there was some mechanism to change it to zero on the second pass, the output would be two. However, the condition `while(0)` is static and false, preventing any subsequent runs after the first.

The incorrect option is (3):
The output cannot be zero times. This choice would be correct only if a standard `while` loop or a `for` loop were used and the condition was initially false. Since the `do-while` loop is designed to execute its body *before* checking the condition, the content of the `do` block is always executed, regardless of whether the `while` condition is true or false. The `do` body is the 'save trees' print statement, which runs at the start.

The incorrect option is (4):
The loop is not infinite. An infinite loop occurs when the controlling condition is perpetually true (e.g., `while(1)` or `while(true)`). In this case, the condition is `while(0)`, which is permanently false. Because the condition is fixed at false, the loop is guaranteed to terminate after its initial, single execution.