For loop in PowerShell - Step-by-Step Execution

Concept Flow - For loop

Initialize i=0

↓

Check: i -lt 5?

No→EXIT

Yes↓

Execute body

↓

Update: i = i + 1

↩Back to Check

The loop starts by setting i to 0, then checks if i is less than 5. If yes, it runs the loop body, then increases i by 1 and repeats. If no, it stops.

Execution Sample

PowerShell

for ($i = 0; $i -lt 5; $i++) {
    Write-Output $i
}

This loop prints numbers from 0 to 4, increasing i by 1 each time until i is no longer less than 5.

Execution Table

Iteration	i	Condition ($i -lt 5)	Action	Output
1	0	True	Print 0, i++	0
2	1	True	Print 1, i++	1
3	2	True	Print 2, i++	2
4	3	True	Print 3, i++	3
5	4	True	Print 4, i++	4
6	5	False	Exit loop

💡 i reaches 5, condition 5 -lt 5 is False, loop stops

Variable Tracker

Variable	Start	After 1	After 2	After 3	After 4	After 5	Final
i	0	1	2	3	4	5	5

Key Moments - 3 Insights

Why does the loop stop when i equals 5?

Because the condition $i -lt 5 becomes False at i=5, as shown in execution_table row 6, so the loop exits.

Does the loop print the number 5?

No, the loop prints numbers only when the condition is True. At i=5, condition is False (row 6), so it does not print 5.

What happens to i after each loop iteration?

i increases by 1 after each iteration, as shown in variable_tracker from 0 up to 5.

Visual Quiz - 3 Questions

Look at the execution table, what is the value of i during iteration 3?

A 2

B 3

C 1

D 0

💡 Hint

Check the 'i' column in execution_table row for iteration 3.

At which iteration does the loop condition become false?

A 5

B 6

C 4

D 1

💡 Hint

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

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

A 5 times

B 4 times

C 6 times

D 7 times

💡 Hint

Think about when $i -le 5 is True, and check variable_tracker for i values.

Concept Snapshot

For loop syntax in PowerShell:
for (<init>; <condition>; <update>) {
  <body>
}
Loop runs while condition is True.
Update runs after each iteration.
Stops when condition is False.

Full Transcript

This PowerShell for loop example starts with i=0. It checks if i is less than 5. If yes, it prints i and then increases i by 1. This repeats until i reaches 5, when the condition becomes false and the loop stops. The output is numbers 0 to 4 printed one by one. The variable i changes from 0 up to 5, increasing by 1 each time. The loop never prints 5 because the condition fails at that point.

Practice

1.

What does a for loop in PowerShell do?

easy

A. Defines a function

B. Runs code only once

C. Stops the script immediately

D. Repeats a block of code a set number of times

Solution

1. Step 1: Understand the purpose of a for loop

   A for loop is designed to repeat code multiple times based on a condition.

2. Step 2: Compare options with the definition

   Only Repeats a block of code a set number of times correctly describes repeating code a set number of times.

3. Final Answer:

   Repeats a block of code a set number of times -> Option D

4. Quick Check:

   For loop = repeat code [OK]

Hint: For loops repeat code multiple times [OK]

Common Mistakes:

• Thinking for loop runs only once
• Confusing for loop with function definition
• Believing for loop stops script

2.

Which of the following is the correct syntax for a for loop in PowerShell?

for (init; condition; increment) { code }

easy

A. for ($i=0; $i -lt 5; $i++) { Write-Output $i }

B. for $i in 0..5 { Write-Output $i }

C. foreach ($i=0; $i -lt 5; $i++) { Write-Output $i }

D. while ($i=0; $i -lt 5; $i++) { Write-Output $i }

Solution

1. Step 1: Identify correct for loop syntax

   PowerShell for loops use parentheses with init; condition; increment separated by semicolons.

2. Step 2: Check each option

   for ($i=0; $i -lt 5; $i++) { Write-Output $i } matches correct syntax. A uses while keyword. B has invalid 'for $i in' syntax. C uses foreach keyword. [OK]

3. Final Answer:

   for ($i=0; $i -lt 5; $i++) { Write-Output $i } -> Option A

4. Quick Check:

   Correct for loop syntax = for ($i=0; $i -lt 5; $i++) { Write-Output $i } [OK]

Hint: For loop uses semicolons inside parentheses [OK]

Common Mistakes:

• Using foreach instead of for
• Using spaces instead of semicolons
• Confusing while loop syntax

3.

What will be the output of this PowerShell code?

for ($i=1; $i -le 3; $i++) { Write-Output ($i * 2) }

medium

A. 0 2 4

B. 1 2 3

C. 2 4 6

D. 3 6 9

Solution

1. Step 1: Understand loop iterations

   The loop runs with $i values 1, 2, and 3 because condition is $i -le 3.

2. Step 2: Calculate output for each iteration

   Output is $i * 2: 1*2=2, 2*2=4, 3*2=6.

3. Final Answer:

   2 4 6 -> Option C

4. Quick Check:

   Multiply each i by 2 = 2 4 6 [OK]

Hint: Multiply loop variable by 2 each iteration [OK]

Common Mistakes:

• Confusing loop range
• Multiplying after loop ends
• Printing loop variable instead of calculation

4.

Identify the error in this PowerShell for loop:

for (; $i < 5; $i++) { Write-Output $i }

medium

A. The increment operator '++' is invalid in PowerShell

B. The loop variable $i is not initialized

C. The condition uses '<' instead of '-lt'

D. The loop body is missing curly braces

Solution

1. Step 1: Check initialization syntax in for loop

   The initialization part is empty; $i needs to be initialized (e.g., $i=0).

2. Step 2: Verify other parts

   Increment '++' is valid, condition '<' works for numbers, braces are present.

3. Final Answer:

   The loop variable $i is not initialized -> Option B

4. Quick Check:

   Always initialize $i in for loop [OK]

Hint: Initialize loop variable in for loop [OK]

Common Mistakes:

• Forgetting to initialize loop variable
• Thinking '++' is invalid
• Using C-style operators like '<' in PowerShell

5.

You want to print only even numbers from 2 to 10 using a for loop in PowerShell. Which code snippet achieves this?

hard

A. for ($i=2; $i -le 10; $i+=2) { Write-Output $i }

B. for ($i=1; $i -lt 10; $i++) { if ($i % 2 -eq 0) { Write-Output $i } }

C. for ($i=2; $i -lt 10; $i++) { Write-Output $i }

D. for ($i=0; $i -le 10; $i+=3) { Write-Output $i }

Solution

1. Step 1: Understand the goal

   We want to print even numbers from 2 to 10 inclusive.

2. Step 2: Analyze each option

   for ($i=1; $i -lt 10; $i++) { if ($i % 2 -eq 0) { Write-Output $i } } goes to i<10 so prints 2,4,6,8 (misses 10). for ($i=2; $i -le 10; $i+=2) { Write-Output $i } starts at 2, increments by 2 up to 10: 2,4,6,8,10. for ($i=2; $i -lt 10; $i++) { Write-Output $i } prints 2-9 all numbers. for ($i=0; $i -le 10; $i+=3) { Write-Output $i } wrong start/step.

3. Final Answer:

   for ($i=2; $i -le 10; $i+=2) { Write-Output $i } -> Option A

4. Quick Check:

   Increment by 2 from 2 to 10 = even numbers [OK]

Hint: Increment by 2 starting at 2 for even numbers [OK]

Common Mistakes:

• Using wrong increment step
• Starting from 1 instead of 2
• Not filtering for even numbers