Loops and Iteration in Pascal

July 22, 2024

Loops and Iteration in Pascal

Welcome back to our Pascal programming course! In this lesson, we will explore loops and iteration in Pascal. Loops are essential for performing repetitive tasks and controlling the flow of a program. By the end of this post, you’ll be able to implement for, while, and repeat-until loops in your Pascal programs.

What are Loops?

Loops allow you to execute a block of code multiple times without having to write the same code repeatedly. This is particularly useful for tasks that require repetition, such as processing items in a list or performing calculations until a certain condition is met.

For Loop

The for loop is used for iterating over a range of values. It is particularly useful when the number of iterations is known beforehand.

The syntax of a for loop in Pascal is as follows:

for variable := start_value to end_value do
begin
    // Code to be executed
end;

Here’s a simple example that prints the numbers from 1 to 5:

program ForLoopExample;
var
    i: Integer;
begin
    for i := 1 to 5 do
    begin
        WriteLn(i);
    end;
end.

While Loop

The while loop is used to execute a block of code as long as a specified condition is true. It is useful when the number of iterations is not known in advance.

The syntax of a while loop in Pascal is as follows:

while condition do
begin
    // Code to be executed
end;

Here’s an example that prints numbers from 1 to 5 using a while loop:

program WhileLoopExample;
var
    i: Integer;
begin
    i := 1;
    while i <= 5 do
    begin
        WriteLn(i);
        i := i + 1;
    end;
end.

Repeat-Until Loop

The repeat-until loop is similar to the while loop, but it guarantees that the code block will be executed at least once before the condition is tested. This is useful when you want to ensure that the loop body runs at least one time.

The syntax of a repeat-until loop in Pascal is as follows:

repeat
    // Code to be executed
until condition;

Here’s an example that prints numbers from 1 to 5 using a repeat-until loop:

program RepeatUntilLoopExample;
var
    i: Integer;
begin
    i := 1;
    repeat
        WriteLn(i);
        i := i + 1;
    until i > 5;
end.

Conclusion

In this lesson, we covered the three main types of loops in Pascal: for, while, and repeat-until. Each type of loop serves its purpose, and understanding when to use each one is crucial for effective programming. Practice implementing these loops in your own programs to solidify your understanding. Happy coding!