........... is an entry controlled loop.

Question

Accepted Answer

The correct option is (1):
The **For** loop is a classic example of an entry-controlled loop, which is also commonly referred to as a pre-test loop. The crucial characteristic of an entry-controlled loop is that the loop's continuation condition is evaluated *before* the block of code inside the loop is executed for any iteration, including the very first one. In the structure of a `for` loop, the initialization, condition, and update are all clearly defined, and the execution begins by checking the condition. If the condition evaluates to false at the start, the loop body is completely bypassed, and the statements inside the loop will not execute even a single time. This pre-check mechanism is the definitive reason why the `for` loop falls under the category of an entry-controlled loop.

The incorrect option is (2):
The **Do while** loop is categorized as an exit-controlled loop or a post-test loop, which is the opposite of an entry-controlled loop. In a `do-while` structure, the loop body is executed first, and the continuation condition is checked only *after* the first iteration. Consequently, the block of code within the `do-while` loop is guaranteed to run at least one time, regardless of whether the controlling condition is initially true or false. This single guaranteed execution before the condition check prevents it from being classified as an entry-controlled loop.

The incorrect option is (3):
**If-then** is a conditional statement, and not an iterative loop structure. Its purpose is to execute a block of code at most once based on a condition, or to select between two courses of action (`if-else`). It enables decision-making and sequential execution, not the repeated or cyclic execution that defines a loop. Since it is a branching construct rather than a mechanism for controlled repetition, it cannot be considered an entry-controlled loop.

The incorrect option is (4):
**Case**, typically implemented as a `switch-case` statement, is a multi-way branching or selection structure. It facilitates choosing one block of code to execute from a set of possible blocks based on the value of an expression. Similar to `if-then`, it is used for selection and executes the chosen code block only once, after which the program flow exits the structure. As it lacks the essential repetitive nature of a loop, it is not considered any type of loop, including an entry-controlled loop.