Delphi FOR Loop Quiz

What is the correct basic structure of a FOR loop in Delphi?

• for i := 1 to 10 do

• for (i = 1; i 0; i--)

• for i = 1 to 10

Answer explanation

The correct FOR loop structure in Delphi is 'for i := 1 to 10 do', which uses ':=' for assignment and 'do' to indicate the start of the loop body. The other options are incorrect syntax for Delphi.

What does this loop do?

• Adds 4 stars to Memo1

• Adds 5 stars to Memo1

• Prints 4 stars in a Label

• Does nothing

Answer explanation

The loop adds 4 stars to Memo1, as indicated by the correct answer choice. It does not print to a label or add 5 stars, and it certainly does not do nothing.

How do you stop a FOR loop early?

• Break;

• Stop;

• ExitLoop;

• Halt;

Answer explanation

To stop a FOR loop early, you use the 'break;' statement. This immediately exits the loop, while the other options like 'Stop;', 'ExitLoop;', and 'Halt;' are not valid commands in most programming languages.

What will the final value of i be after this loop?

• i will be undefined (loop variable cannot be relied on after loop)

• 6

• 5

• 0

Answer explanation

In many programming languages, the loop variable 'i' is scoped to the loop itself. After the loop ends, 'i' is no longer accessible, leading to it being undefined. Therefore, the correct answer is that 'i will be undefined (loop variable cannot be relied on after loop)'.

Which component can be used to display FOR loop output line by line?

• Memo

• Label

• Button

• Image

Answer explanation

The Memo component is ideal for displaying text output line by line, making it suitable for showing results from a FOR loop. In contrast, Label and Image are not designed for multiline text, and Button is for user interaction.

What does this loop print?

• 13

• 123

• 12

• 23

Answer explanation

The loop prints '1' and '3' sequentially without spaces, resulting in '13'. Therefore, the correct answer is 13.

What does the following loop do?

• Adds 5 items to the ListBox

• Adds 1 item

• Replaces ListBox items

• Clears ListBox

Answer explanation

The loop iterates five times, adding an item to the ListBox during each iteration. Therefore, it adds a total of 5 items to the ListBox, making 'Adds 5 items to the ListBox' the correct choice.

Which statement is true about loop bounds in Delphi?

• The TO value must be greater than or equal to the FROM value for 'to' loops.

• You can use strings in a FOR loop counter.

• FOR loops can run forever by default.

• Loop variables can be modified inside the loop.

Answer explanation

In Delphi, the 'to' value in a FOR loop must be greater than or equal to the 'from' value to ensure the loop executes correctly. This makes the first statement true, while the others are incorrect.

What happens if you try this?

• You get unexpected behavior because loop variable should not be modified

• It runs 3 times as normal

• It shows an error message

• It runs once only

Answer explanation

Modifying the loop variable can lead to unexpected behavior, as it disrupts the intended control flow of the loop. This is why the correct choice is that you get unexpected behavior because the loop variable should not be modified.

How can you display all even numbers from 2 to 10 using a FOR loop?

• for i := 2 to 10 do if i mod 2 = 0 then ShowMessage(IntToStr(i));

• for i := 2 to 10 step 2 do

• for even i := 2 to 10 do

• for i := 2 until 10 even

Answer explanation

The correct choice uses a FOR loop to iterate from 2 to 10, checking if each number is even with 'i mod 2 = 0'. This effectively displays all even numbers in that range, making it the right solution.