Loop execution flow in C++ - Step-by-Step Execution

Concept Flow - Loop execution flow

Initialize loop variable

↓

Check loop condition

No→Exit loop

Yes↓

Execute loop body

↓

Update loop variable

↩Back to Check loop condition

This flow shows how a loop starts by setting a variable, checks a condition, runs the loop body if true, updates the variable, and repeats until the condition is false.

Execution Sample

C++

for (int i = 0; i < 3; i++) {
    std::cout << i << std::endl;
}

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

Execution Table

Iteration	i	Condition (i < 3)	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	false	Exit loop

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

Variable Tracker

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

Key Moments - 3 Insights

Why does the loop stop when i equals 3?

Because the condition i < 3 becomes false at iteration 4 (see execution_table row 4), so the loop exits.

When is the variable i updated during the loop?

i is updated after the loop body executes in each iteration (see execution_table Action column), before the next condition check.

What happens if the initial condition is false?

The loop body does not run at all and the loop exits immediately (not shown here but implied by the flow).

Visual Quiz - 3 Questions

Look at the execution_table, what is the value of i at iteration 2?

A 0

B 2

C 1

D 3

💡 Hint

Check the 'i' column in execution_table row for iteration 2.

At which iteration does the loop condition become false?

A Iteration 4

B Iteration 3

C Iteration 1

D Iteration 2

💡 Hint

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

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

A 3 times

B 5 times

C 4 times

D 6 times

💡 Hint

The loop runs while i is less than the limit; check variable_tracker for i values.

Concept Snapshot

for (init; condition; update) {
  // loop body
}

1. Initialize variable
2. Check condition
3. Run body if true
4. Update variable
5. Repeat until condition false

Full Transcript

This example shows a for loop in C++ starting with i=0. Each step checks if i is less than 3. If yes, it prints i, then increases i by 1. This repeats until i reaches 3, when the condition fails and the loop stops. The variable i changes from 0 to 3 over the iterations. Key points are when the condition is checked and when i updates. The loop runs exactly three times, printing 0, 1, and 2.