For loop with step and downTo in Kotlin - Step-by-Step Execution

Concept Flow - For loop with step and downTo

Initialize i = start

↓

Check: i >= end?

No→EXIT

Yes↓

Execute loop body

↓

Update: i = i - step

↩Back to Check

The loop starts at a number and counts down to an end number, decreasing by a step each time, running the loop body while the condition is true.

Execution Sample

Kotlin

for (i in 10 downTo 2 step 2) {
    println(i)
}

Prints numbers from 10 down to 2, decreasing by 2 each time.

Execution Table

Iteration	i value	Condition (i >= 2)	Action	Output
1	10	True	Print 10	10
2	8	True	Print 8	8
3	6	True	Print 6	6
4	4	True	Print 4	4
5	2	True	Print 2	2

💡 After printing 2, the next value would be 0 which is less than 2, so the loop stops.

Variable Tracker

Variable	Start	After 1	After 2	After 3	After 4	After 5	Final
i	10	8	6	4	2

Key Moments - 2 Insights

Why does the loop stop when i is 0 even though 0 is less than 2?

The loop condition is i >= 2. When i becomes 0, 0 >= 2 is false, so the loop stops as shown in execution_table after the last printed value.

How does the step 2 affect the values of i?

The step 2 means i decreases by 2 each time (10, 8, 6, ...). This is shown in variable_tracker where i changes by -2 each iteration.

Visual Quiz - 3 Questions

Look at the execution_table, what is the value of i at iteration 3?

A 8

B 6

C 4

D 2

💡 Hint

Check the 'i value' column at iteration 3 in the execution_table.

At which iteration does the loop condition become false?

A 5

B 4

C 6

D 7

💡 Hint

Look at the 'Condition' column in execution_table where it becomes False.

If the step was changed to 3, what would be the value of i at iteration 2?

A 7

B 6

C 5

D 8

💡 Hint

With step 3, i decreases by 3 each time: 10, 7, 4... Check variable_tracker logic.

Concept Snapshot

for (i in start downTo end step stepValue) {
  // loop body
}

- Counts down from start to end (inclusive)
- Decreases i by stepValue each time
- Stops when i < end
- Useful for reverse loops with custom steps

Full Transcript

This visual execution shows how a Kotlin for loop with downTo and step works. The loop starts at 10 and counts down to 2, decreasing by 2 each time. Each iteration checks if i is still greater or equal to 2. If yes, it runs the loop body and prints i. Then i decreases by 2. When i becomes less than 2, the condition fails and the loop stops. The variable tracker shows i's value after each iteration. Key moments clarify why the loop stops and how step affects i. The quiz tests understanding of i's values and loop stopping point.