In C, what will be the output of the following program that combines a for loop, a while loop, a do while loop and the continue statement? #include <stdio.h> int main(void) { int i; for (i = 10; i <= 15; i++) { while (i) { do { printf("%d ", 1); if (i > 1) continue; } while (0); break; } } return 0; }

Introduction / Context:
This question tests detailed understanding of C control flow constructs, especially the interaction of nested loops and the continue and break statements. It is easy to misinterpret which loop a particular continue or break affects. The code uses a for loop around a while loop, and inside the while there is a do while loop that always executes exactly once because its condition is zero. Careful analysis of which loop each control statement targets is required to determine the correct output.

Given Data / Assumptions:

• The outer loop is for (i = 10; i <= 15; i++).
• The inner loop is while (i) which executes while i is nonzero.
• Inside while, there is a do { ... } while (0); which always executes its body once.
• The do body prints 1 followed by a space and then conditionally executes continue.
• A break statement immediately follows the do while inside the while loop.

Concept / Approach:
The key detail is that continue applies to the nearest enclosing loop, which in this case is the do while loop, not the while or the for loop. Because the do while condition is fixed at zero, the continue simply jumps to the end of the do block and then evaluates while (0), which terminates the do loop. After the do loop finishes, the break statement is executed in the surrounding while, causing exit from that while loop. The outer for loop then increments i and repeats. Therefore, the nested loops execute a single printf for each iteration of the for loop and do not create an infinite loop.

Step-by-Step Solution:
Step 1: For i = 10, the while (i) condition is true, so execution enters the while loop. Step 2: The do block prints "1 " and sees that i > 1, so it executes continue, which applies to the do while loop. Step 3: continue skips to the while (0) test, which is false, so the do while loop terminates. Step 4: Control reaches the break statement inside while, which exits the while loop. Step 5: The for loop increments i to 11 and the same logic repeats for i = 11, 12, 13, 14 and 15, each time printing "1 " exactly once.

Verification / Alternative check:
Counting iterations, the outer for loop runs for i values 10, 11, 12, 13, 14 and 15, which is six iterations. In each iteration, the body prints "1 " exactly once before break terminates the while loop. There is no path through the code that allows more than one execution of printf per for iteration because break is unconditional and always reached. Running an equivalent program in an environment will confirm that the output line consists of six ones separated by spaces.

Why Other Options Are Wrong:
Option B claims an infinite loop, which would require a continue that targets the while or for loop, but here it targets only the do loop, which is controlled by while (0) and always exits. Option C suggests no output, which would require printf never to execute, but it clearly does so on every for iteration. Option D accounts for only two ones, ignoring that the outer for loop repeats six times, not two.

Common Pitfalls:
Many programmers mistakenly think that continue affects the outermost loop instead of the innermost loop. Another common confusion is forgetting how do while loops work, especially when the condition is constant false. It is also easy to overlook that i is never changed inside the while except by the for loop, so while (i) would be infinite without the break. Carefully matching each continue and break to its loop avoids such errors in both exams and production code.

Final Answer:
The program prints 1 followed by a space six times, producing the output 1 1 1 1 1 1 .