Understanding the Basic Control Structures

What are the three basic control structures mentioned in the text?

• Sequence, Selection, Iteration

• Input, Process, Output

• Data, Information, Knowledge

• Analysis, Design, Implementation

Answer explanation

The three basic control structures in programming are Sequence, Selection, and Iteration. Sequence refers to executing statements in order, Selection involves making decisions, and Iteration is about repeating actions.

Which control structure is described as having lines of code follow in order one after the other?

Answer explanation

The control structure described is 'sequential execution', where lines of code are executed one after the other in the order they appear. This is the default mode of execution in most programming languages.

In a flowchart, how is binary selection shown?

• Using a diamond shape

• Using a rectangle shape

• Using a circle shape

• Using a parallelogram shape

Answer explanation

In a flowchart, binary selection is represented using a diamond shape. This shape indicates a decision point where the flow can branch into two paths based on a yes/no or true/false condition.

What is the most important control structure that allows a computer to repeat actions effortlessly many times?

Answer explanation

The most important control structure for repeating actions is the loop. Loops, such as 'for' and 'while', allow a computer to execute a block of code multiple times without manual intervention, making repetitive tasks efficient.

Explain the difference between pre-test loops and post-test loops.

• Pre-test loops check the condition before executing the loop body, while post-test loops check the condition after executing the loop body.

• Pre-test loops check the condition after executing the loop body, while post-test loops check the condition before executing the loop body.

• Both pre-test and post-test loops check the condition before executing the loop body.

• Both pre-test and post-test loops check the condition after executing the loop body.

Answer explanation

Pre-test loops evaluate the condition before the loop body runs, ensuring the loop may not execute at all if the condition is false. In contrast, post-test loops execute the loop body first and then check the condition, guaranteeing at least one execution.

Fill in the blank: A pre-test loop performs a test ______ starting on the loop.

• condition

• iteration

• execution

• termination

Answer explanation

A pre-test loop checks a condition before executing the loop body. This means it evaluates whether to enter the loop based on the specified condition, making 'condition' the correct choice.

What does the loop do when the test condition evaluates to False?

Answer explanation

When the test condition evaluates to False, the loop terminates and control passes to the next statement following the loop. No further iterations occur.

A post-test loop is a type of loop that:

• executes the loop body at least once before checking the condition.

• checks the condition before executing the loop body.

• does not execute if the condition is false initially.

• executes indefinitely without a condition.

Answer explanation

A post-test loop, like a do-while loop, executes the loop body at least once before checking the condition. This distinguishes it from pre-test loops, which check the condition first.

Which of the following statements is true about post-test loops?

• A) The loop test condition is evaluated before the loop action.

• B) The loop test condition is evaluated after the loop action.

• C) The loop never terminates.

• D) The loop test condition is never evaluated.

Answer explanation

In post-test loops, the loop action is executed first, and then the test condition is evaluated. This means that the correct choice is B, as the condition is checked after the loop action has taken place.

Explain the difference between pre-test and post-test loops using the example of eating a bag of chips.

• Pre-test loops check the condition before executing the loop, while post-test loops check the condition after executing the loop.

• Pre-test loops are used for eating chips, while post-test loops are used for drinking soda.

• Pre-test loops and post-test loops are the same and can be used interchangeably.

• Pre-test loops are only used in programming, while post-test loops are used in real life scenarios.

Answer explanation

Pre-test loops evaluate the condition before the loop starts, like checking if you want to eat chips before grabbing the bag. Post-test loops check after the loop, similar to deciding if you want more chips after finishing the bag.