Types of loops in computer programming — simple guide for an 11-year-old

What is a loop?

A loop is a way for a computer to repeat the same steps again and again until something tells it to stop. It is like telling a robot: "Do this task 5 times" or "Keep doing this until I say stop."

Common types of loops

• 1) For loop (counting loop)

  Use when you know how many times you want to repeat something (for example, 5 times).

  for i from 1 to 5:
      print('Hello', i)

  This will print Hello 1, Hello 2, ... Hello 5.

• 2) While loop (condition loop)

  Use when you want to repeat as long as a condition is true. The condition is checked before each repeat.

  count = 1
  while count <= 5:
      print('Hi', count)
      count = count + 1

  This also prints Hi 1 through Hi 5.

• 3) Do-while loop (do then check)

  Some languages have a loop that always runs the block at least once, then checks the condition to decide whether to repeat.

  do {
      print('Hey')
      count = count + 1
  } while (count <= 5)

  This will run the block, then check if it should run again.

• 4) For-each loop (loop over items)

  Use when you want to do something to every item in a list, array, or collection.

  for fruit in ['apple', 'banana', 'cherry']:
      print(fruit)

  This prints each fruit in the list, one by one.

Other important loop ideas

• Nested loops

  A nested loop is a loop inside another loop. Use when you need to repeat a set of steps for each item of another set (for example, rows and columns).

  for row from 1 to 3:
      for col from 1 to 2:
          print('cell', row, col)

  This prints cell positions like (1,1), (1,2), (2,1), ...

• Infinite loops

  An infinite loop never stops by itself. Example: while True: in Python. Infinite loops are usually a bug unless you really want the program to run forever (like a game loop). You must include a way to stop it.

  while True:
      do_something()
      if user_wants_to_stop:
          break

• Break and continue

  These commands change loop behavior:

  • break: stops the whole loop right away.
  • continue: skips the rest of the current loop repeat and moves to the next one.

  for i from 1 to 10:
      if i == 5:
          break   # stops the loop when i is 5
  
  for i from 1 to 10:
      if i % 2 == 0:
          continue   # skips even numbers

Quick tips

• Choose a for loop when you know how many repeats you want.
• Choose a while loop when you repeat until a condition changes.
• Watch out for infinite loops. Make sure the condition will eventually become false or include a break.
• Use nested loops carefully — they can make programs slow if they run many times.

Try these practice tasks

1. Write a loop that prints numbers 1 to 10.
2. Write a loop that prints only even numbers from 2 to 20.
3. Use a nested loop to print a 3 by 3 grid of stars (*) like a small square.

If you want, tell me which programming language you are using (like Python, Scratch, or JavaScript) and I will give you exact code examples for that language.