While loops in MATLAB - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a while loop that runs as long as x is less than 5.

MATLAB

x = 1;
while [1]
    disp(x);
    x = x + 1;
end

Drag options to blanks, or click blank then click option'

Ax > 5

Bx < 5

Cx == 5

Dx >= 5

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'x > 5' which never becomes true initially.

Using 'x == 5' which runs only when x equals 5.

Using 'x >= 5' which is false at start.

The condition x < 5 makes the loop run while x is less than 5.

2fill in blank

medium

Complete the code to stop the loop when the variable 'count' reaches 10.

MATLAB

count = 0;
while [1]
    count = count + 1;
    disp(count);
end

Drag options to blanks, or click blank then click option'

Acount < 10

Bcount ~= 10

Ccount > 10

Dcount == 10

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'count == 10' which runs only when count equals 10.

Using 'count > 10' which is false at start.

Using 'count ~= 10' which runs when count is not 10, causing an extra iteration.

The loop continues while count < 10, stopping when count reaches 10.

3fill in blank

hard

Fix the error in the while loop condition to avoid an infinite loop.

MATLAB

num = 5;
while [1]
    disp(num);
    num = num - 1;
end

Drag options to blanks, or click blank then click option'

Anum > 0

Bnum >= 5

Cnum == 5

Dnum < 0

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'num == 5' which never changes inside the loop.

Using 'num >= 5' which is true initially but false after decrement.

Using 'num < 0' which is false at start.

The condition num > 0 ensures the loop stops when num reaches 0, preventing infinite looping.

4fill in blank

hard

Fill both blanks to create a while loop that prints numbers from 1 to 5.

MATLAB

i = 1;
while [1]
    disp(i);
    i = i [2] 1;
end

Drag options to blanks, or click blank then click option'

Ai <= 5

Bi < 5

C+

D-

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'i < 5' which stops before printing 5.

Using '-' operator which decreases i causing infinite loop.

The loop runs while i <= 5 and increments i by 1 each time.

5fill in blank

hard

Fill all three blanks to create a while loop that sums numbers from 1 to 5.

MATLAB

sum = 0;
i = 1;
while [1]
    sum = sum + i;
    i = i [2] 1;
end
result = sum [3] 15;

Drag options to blanks, or click blank then click option'

Ai <= 5

B+

C==

D<

Attempts:

3 left

💡 Hint

Common Mistakes

Using '<' instead of '<=' causing missing last number.

Using '-' operator decreasing i causing infinite loop.

Using '=' instead of '==' for comparison.

The loop runs while i <= 5, adds i to sum, increments i by 1, and checks if sum equals 15.

Practice

1. What does a while loop do in MATLAB?

easy

A. Repeats a block of code as long as a condition is true

B. Executes code only once

C. Runs code a fixed number of times

D. Stops the program immediately

Solution

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

   A while loop runs repeatedly while its condition remains true.

2. Step 2: Compare options with definition

   Only Repeats a block of code as long as a condition is true correctly describes this behavior.

3. Final Answer:

   Repeats a block of code as long as a condition is true -> Option A

4. Quick Check:

   While loop = repeat while true [OK]

Hint: While loops run while condition is true, not fixed times [OK]

Common Mistakes:

• Thinking while loops run a fixed number of times
• Confusing while with if statement
• Believing while loops run only once

2. Which of the following is the correct syntax for a while loop in MATLAB?

easy

A. while condition
statements
end

B. while (condition) {
statements
}

C. while condition:
statements
end

D. while condition do
statements
end

Solution

1. Step 1: Recall MATLAB while loop syntax

   MATLAB uses 'while condition' followed by statements and ends with 'end'.

2. Step 2: Check each option

   while condition statements end matches MATLAB syntax; others use syntax from other languages.

3. Final Answer:

   while condition\n statements\nend -> Option A

4. Quick Check:

   MATLAB uses 'end' to close loops [OK]

Hint: MATLAB while loops end with 'end', no braces [OK]

Common Mistakes:

• Using braces {} instead of 'end'
• Adding colons after condition
• Using 'do' keyword

3. What will be the output of this MATLAB code?

i = 1;
while i <= 3
  disp(i)
  i = i + 1;
end

medium

A. 1 2 3 4

B. 1 2 3

C. 1 2

D. Error: infinite loop

Solution

1. Step 1: Analyze loop condition and increments

   The loop runs while i is less than or equal to 3, starting at 1 and increasing by 1 each time.

2. Step 2: Trace output values

   Values displayed are 1, then 2, then 3. When i becomes 4, condition fails and loop stops.

3. Final Answer:

   1 2 3 -> Option B

4. Quick Check:

   Loop prints 1 to 3 [OK]

Hint: Increment loop variable to avoid infinite loop [OK]

Common Mistakes:

• Forgetting to increment i causing infinite loop
• Expecting output to include 4
• Confusing loop condition with < instead of <=

4. Identify the error in this MATLAB code snippet:

count = 5;
while count > 0
  disp(count)
end

medium

A. disp function cannot be used inside while

B. Incorrect while syntax

C. Missing increment or decrement inside the loop

D. Variable 'count' not initialized

Solution

1. Step 1: Check loop condition and body

   The loop condition is 'count > 0', but inside the loop count is never changed.

2. Step 2: Understand effect of missing update

   Without changing count, the condition stays true forever, causing an infinite loop.

3. Final Answer:

   Missing increment or decrement inside the loop -> Option C

4. Quick Check:

   Update loop variable to avoid infinite loop [OK]

Hint: Always update loop variable inside while loop [OK]

Common Mistakes:

• Forgetting to change loop variable
• Assuming disp causes error
• Thinking syntax is wrong

5. Write a MATLAB while loop that sums numbers from 1 to 10 and stores the result in total. Which code correctly does this?

hard

A. total = 0;
i = 1;
while i <= 10
total = total + i;
i = i - 1;
end

B. total = 0;
i = 1;
while i < 10
total = total + i;
end

C. total = 0;
for i = 1:10
total = total + i;
end

D. total = 0;
i = 1;
while i <= 10
total = total + i;
i = i + 1;
end

Solution

1. Step 1: Understand the goal and loop condition

   We want to add numbers 1 through 10 using a while loop that stops when i > 10.

2. Step 2: Check each option for correctness

   total = 0; i = 1; while i <= 10 total = total + i; i = i + 1; end initializes total and i, adds i to total, increments i, and stops at 10 correctly. total = 0; i = 1; while i < 10 total = total + i; end misses increment causing infinite loop. total = 0; for i = 1:10 total = total + i; end uses for loop, not while. total = 0; i = 1; while i <= 10 total = total + i; i = i - 1; end decrements i causing infinite loop.

3. Final Answer:

   total = 0;\ni = 1;\nwhile i <= 10\n total = total + i;\n i = i + 1;\nend -> Option D

4. Quick Check:

   Increment i to sum 1 to 10 [OK]

Hint: Increment loop variable to reach end condition [OK]

Common Mistakes:

• Forgetting to increment i
• Using for loop instead of while
• Decrementing i causing infinite loop