Question

A loop that evaluates its test expression before each repetition is a(n) ____________ loop.

Short answer

Answer: A while loop.

Step-by-step solution

Identify the types of loops

There are two main types of loops in programming languages: "for" loops and "while" loops. Both of these loops evaluate the test expression before executing the loop body. In this case, we will focus on the "while" loop since it is commonly known for its test expression evaluation before each repetition.

Choose the correct loop type

Considering the description in the exercise, the correct type of loop that evaluates its test expression before each repetition is a "while" loop.

Conclusion

A loop that evaluates its test expression before each repetition is a(n) while loop.

Key concepts

Programming Loops

Programming loops are foundational structures in computer programming that allow us to execute a block of code multiple times. This is incredibly useful whenever we want to repeat an operation without writing the same lines of code over and over again.

There are various types of loops, but the most common ones are 'for' loops and 'while' loops. The 'for' loop is used when we know in advance how many times we want to execute a block of code, for instance, iterating over the elements of an array. A 'while' loop, on the other hand, keeps running as long as a given condition, known as the test expression, remains true. This makes it ideal for scenarios where the number of iterations is not known beforehand, like reading a file until the end is reached.

Test Expression Evaluation

A test expression is a logical statement that is evaluated before each iteration of a loop. The outcome of this evaluation determines whether the loop will execute its body of code or not.

In a 'while' loop, the test expression is checked prior to each iteration. If the expression evaluates to 'true', the loop continues and executes its body. If, however, the expression evaluates to 'false', the loop stops, and the program flow moves onto whatever code comes next. This mechanism allows the loop to react dynamically to changing conditions within the program, like updated variable values, making it a powerful tool for controlling the flow of execution.

Loop Control Structures

Loop control structures are elements within programming that manage the execution of loops. In the case of 'while' loops, two principal control statements are of note: 'break' and 'continue'.

Using 'break' within a 'while' loop immediately stops the loop and transfers control to the next statement following the loop body. It's typically used when an external condition is met during iteration. Alternatively, 'continue' halts the current iteration and immediately begins the next, effectively skipping any code following it within the body for the current iteration. Both of these control statements provide developers with a precise degree of control over how and when a loop should terminate or proceed to the next iteration.