Why control flow directs program logic in MATLAB - Test Your Understanding

Practice - 5 Tasks

1fill in blank

easy

Complete the code to check if a number is positive.

MATLAB

if [1] > 0
    disp('Positive number');
end

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

Ax

Bvalue

Cnum

Dnumber

Attempts:

3 left

💡 Hint

Common Mistakes

Using a variable name not defined in the code.

The variable num is used to check if it is greater than zero.

2fill in blank

medium

Complete the code to execute the else block when the number is not positive.

MATLAB

if num > 0
    disp('Positive');
[1]
    disp('Not positive');
end

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

Aelseif num <= 0

Belseif

Cendif

Delse

Attempts:

3 left

💡 Hint

Common Mistakes

Using elseif without a condition.

The else keyword runs the code when the if condition is false.

3fill in blank

hard

Fix the error in the loop to print numbers from 1 to 5.

MATLAB

for i = 1:[1]
    disp(i);
end

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

A5

B0

C6

D10

Attempts:

3 left

💡 Hint

Common Mistakes

Using 0 or 6 as the upper limit.

The loop should run from 1 to 5, so the upper limit is 5.

4fill in blank

hard

Fill both blanks to create a loop that prints even numbers from 2 to 10.

MATLAB

for num = [1]:[2]:10
    disp(num);
end

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

A2

B1

D3

Attempts:

3 left

💡 Hint

Common Mistakes

Using 1 as the step value, which prints all numbers.

The loop starts at 2 and increments by 2 to print even numbers.

5fill in blank

hard

Fill all three blanks to create a conditional that prints 'Even' or 'Odd' for a number.

MATLAB

if mod([1], [2]) == [3]
    disp('Even');
else
    disp('Odd');
end

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

Anum

B2

C0

D1

Attempts:

3 left

💡 Hint

Common Mistakes

Using 1 as the remainder to check for even numbers.

The mod function checks if num divided by 2 has remainder 0 (even).

Practice

1. What is the main purpose of control flow statements like if and for in MATLAB?

easy

A. To display messages on the screen

B. To decide which parts of the code run and how many times

C. To create new functions

D. To store data in variables

Solution

1. Step 1: Understand control flow role

   Control flow statements let the program choose actions or repeat tasks.

2. Step 2: Identify main purpose

   They control which code runs and how often, unlike storing data or displaying messages.

3. Final Answer:

   To decide which parts of the code run and how many times -> Option B

4. Quick Check:

   Control flow = decide actions and repetitions [OK]

Hint: Control flow controls decisions and loops [OK]

Common Mistakes:

• Confusing control flow with data storage
• Thinking control flow creates functions
• Believing control flow only displays output

2. Which of the following is the correct syntax for an if statement in MATLAB?

easy

A. if x > 5
disp('Greater')
end

B. if (x > 5) {
disp('Greater');
}

C. if x > 5 then
disp('Greater')
endif

D. if x > 5:
disp('Greater')

Solution

1. Step 1: Recall MATLAB if syntax

   MATLAB uses if condition followed by code and ends with end.

2. Step 2: Compare options

   if x > 5 disp('Greater') end matches MATLAB syntax; others use syntax from other languages.

3. Final Answer:

   if x > 5 disp('Greater') end -> Option A

4. Quick Check:

   MATLAB if ends with end [OK]

Hint: MATLAB if ends with 'end' keyword [OK]

Common Mistakes:

• Using curly braces {} like C or Java
• Using 'then' or 'endif' like other languages
• Using colon : like Python

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

for i = 1:3
  if i == 2
    disp('Two')
  else
    disp(i)
  end
end

medium

A. Error: Missing end statement

B. 1\n2\n3

C. Two\nTwo\nTwo

D. 1\nTwo\n3

Solution

1. Step 1: Trace the loop iterations

   Loop runs i = 1, 2, 3.

2. Step 2: Check conditions and output

   When i=1, else runs: displays '1'. When i=2, if runs: displays 'Two'. When i=3, else runs: displays '3'.

3. Final Answer:

   1\nTwo\n3 -> Option D

4. Quick Check:

   Loop with if-else outputs 1, Two, 3 [OK]

Hint: Check each loop step and condition carefully [OK]

Common Mistakes:

• Assuming all outputs are numbers
• Forgetting else runs when if is false
• Thinking code has syntax error

4. Identify the error in this MATLAB code snippet:

count = 0;
while count < 3
  disp(count)
  count = count + 1
end
end

medium

A. Incorrect while loop condition syntax

B. Missing semicolon after count increment

C. Extra 'end' keyword at the end

D. disp function used incorrectly

Solution

1. Step 1: Check loop structure

   The while loop starts with 'while' and must end with one 'end'.

2. Step 2: Identify extra 'end'

   There are two 'end' statements but only one loop, so one 'end' is extra and causes error.

3. Final Answer:

   Extra 'end' keyword at the end -> Option C

4. Quick Check:

   One loop needs one end [OK]

Hint: Count 'end' statements to match blocks [OK]

Common Mistakes:

• Thinking semicolon is mandatory after every line
• Assuming while condition syntax is wrong
• Believing disp needs special syntax

5. You want to write MATLAB code that prints all even numbers from 2 to 10 using a for loop and if condition. Which code correctly uses control flow to do this?

hard

A. for i = 2:10
if mod(i,2) == 0
disp(i)
end
end

B. for i = 2:2:10
disp(i)
end

C. for i = 1:10
if i/2 == 0
disp(i)
end
end

D. for i = 2:10
if i % 2 == 0
disp(i)
end
end

Solution

1. Step 1: Understand the task

   Print even numbers 2 to 10 using for loop and if condition.

2. Step 2: Check each option

   for i = 2:10 if mod(i,2) == 0 disp(i) end end uses mod(i,2)==0 correctly to check even numbers. for i = 2:2:10 disp(i) end skips if but uses step 2 in loop (valid but no if). for i = 1:10 if i/2 == 0 disp(i) end end uses wrong condition i/2==0 (always false). for i = 2:10 if i % 2 == 0 disp(i) end end uses % operator which is not MATLAB syntax.

3. Final Answer:

   for i = 2:10 if mod(i,2) == 0 disp(i) end end -> Option A

4. Quick Check:

   mod(i,2)==0 checks even numbers [OK]

Hint: Use mod(i,2)==0 to test even numbers in MATLAB [OK]

Common Mistakes:

• Using % instead of mod for remainder
• Wrong condition like i/2 == 0
• Skipping if when required