While loop in Ruby - Step-by-Step Execution

Concept Flow - While loop

Initialize variable

↓

Check condition

|Yes↓

Execute loop body

↓

Update variable

Back to Check↓

Exit loop

↩Back to Check

The while loop starts by checking a condition. If true, it runs the loop body, updates variables, then checks again. It stops when the condition is false.

Execution Sample

Ruby

i = 0
while i < 3
  puts i
  i += 1
end

This code prints numbers 0, 1, and 2 by looping while i is less than 3.

Execution Table

Step	i	Condition (i < 3)	Action	Output
1	0	true	Print 0, i = i + 1	0
2	1	true	Print 1, i = i + 1	1
3	2	true	Print 2, i = i + 1	2
4	3	false	Exit loop

💡 i reaches 3, condition 3 < 3 is false, loop stops

Variable Tracker

Variable	Start	After 1	After 2	After 3	Final
i	0	1	2	3	3

Key Moments - 2 Insights

Why does the loop stop when i equals 3?

Because the condition i < 3 becomes false at step 4, so the loop does not run again (see execution_table row 4).

What happens if we forget to update i inside the loop?

The condition stays true forever, causing an infinite loop. The variable i must change to eventually make the condition false.

Visual Quiz - 3 Questions

Look at the execution table, what is the value of i at step 2?

A 2

B 0

C 1

D 3

💡 Hint

Check the 'i' column in execution_table row 2.

At which step does the condition become false and the loop stops?

A Step 4

B Step 3

C Step 1

D Step 2

💡 Hint

Look at the 'Condition' column in execution_table where it changes to false.

If we change the condition to i < 5, how many times will the loop run?

A 3 times

B 5 times

C 4 times

D 6 times

💡 Hint

Refer to variable_tracker and how i increments until condition is false.

Concept Snapshot

while condition do
  # code to repeat
  update variables
end

- Checks condition before each loop
- Runs body only if condition true
- Stops when condition false
- Update variables inside to avoid infinite loop

Full Transcript

This visual shows how a while loop works in Ruby. We start with i = 0. The loop checks if i is less than 3. If yes, it prints i and adds 1 to i. This repeats until i reaches 3, when the condition becomes false and the loop stops. The variable i changes from 0 to 3 step by step. If we forget to update i, the loop never ends. Changing the condition changes how many times the loop runs.