Control Statements : MCQs & PYQs with Explanation

Option D

The given C++ code is:
int j, n;
for(j = 1; j <= n;)
    j = j * 2;
Here, the value of j starts from 1 and becomes twice its previous value after every iteration. The values of j will be, 1 → 2 → 4 → 8 → 16 → 32 → and so on.
In each iteration, j is multiplied by 2. Therefore, after k iterations: j=2^k
The loop continues until j becomes greater than n. Therefore, the number of iterations is approximately: log₂ n+1

For example, if n=8:

So, the loop executes 4 times.
Using the formula: log₂ 8+1 = 3+1 = 4
Therefore, the number of iterations is log₂ n+1.

Option C

Here, the important point is the comma operator used in the for-loop condition.
for(a=1,b=1; a<5,b<10; b++)
    cout << a;
In a for loop, the condition part can use the comma operator (,). When the comma operator is used, all expressions are evaluated, but the result of the last expression decides the loop condition.

• The a<5 is evaluated but its result is ignored.
• The b<10 is the last expression, so it controls the loop.
• The a is initialized to 1 and is never changed inside the loop.
• The b starts from 1 and is incremented each iteration.
• The loop runs as long as b<10, i.e., for b=1 to 9.
• Each time, cout<<a; prints the value of a, which is always 1.