MATLAB Desktop and Command Window - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of Command Window Variable Display

What will be displayed in the MATLAB Command Window after running this code?

MATLAB

x = 5;
disp(x + 3);

A x + 3

B 5 + 3

C 8

D Error: Undefined function or variable 'x + 3'.

💡 Hint

The disp function shows the value of the expression inside it.

The variable x is assigned 5. disp(x + 3) calculates 5 + 3 and displays 8.

🧠 Conceptual

intermediate

Understanding Command Window Behavior

Which statement about the MATLAB Command Window is true?

A It only shows output when the semicolon is omitted at the end of a command.

B It automatically saves all commands to a file.

C It cannot display text messages using disp or fprintf.

D It requires restarting MATLAB to clear previous outputs.

💡 Hint

Think about how MATLAB shows or hides output after commands.

In MATLAB, ending a command with a semicolon suppresses output in the Command Window. Without it, MATLAB displays the result.

🔧 Debug

advanced

Identify the Error in Command Window Input

What error will MATLAB show when running this command in the Command Window?

MATLAB

y = 10
z = y + 5;

A Error: Undefined variable 'y'.

B Error: Unexpected end of statement.

C Error: Missing semicolon after first line.

D No error; y is assigned 10 and z is assigned 15.

💡 Hint

Check if omitting semicolon causes an error or just output.

In MATLAB, omitting a semicolon does not cause an error; it only shows output. Both assignments are valid.

❓ Predict Output

advanced

Command Window Output with fprintf

What is the output in the Command Window after running this code?

MATLAB

a = 7;
fprintf('Value of a is %d\n', a);

A Error: Invalid format specifier.

B Value of a is 7

C 7

D Value of a is %d

💡 Hint

fprintf prints formatted text to the Command Window.

The %d is replaced by the value of a (7), so the output is 'Value of a is 7'.

🧠 Conceptual

expert

Command Window Variable Persistence

After running a script that defines variable x = 10 in the Command Window, what happens to x if you clear the Command Window using the 'clc' command?

A Variable x remains in memory and can be used.

B Variable x is reset to zero.

C Variable x is deleted and no longer exists.

D Variable x is saved to a file automatically.

💡 Hint

Think about what 'clc' does versus 'clear'.

'clc' clears the Command Window text but does not remove variables from memory. 'clear' removes variables.

Practice

1. What is the primary purpose of the MATLAB Command Window?

easy

A. To type commands and see immediate results

B. To write and save large programs only

C. To manage files and folders on your computer

D. To create graphical user interfaces

Solution

1. Step 1: Understand the role of the Command Window

   The Command Window is designed for typing commands and instantly seeing their output.

2. Step 2: Compare with other MATLAB features

   Writing large programs is done in the Editor, file management is outside MATLAB, and GUIs are created with special tools.

3. Final Answer:

   To type commands and see immediate results -> Option A

4. Quick Check:

   Command Window = Immediate command input and output [OK]

Hint: Command Window shows instant results of typed commands [OK]

Common Mistakes:

• Confusing Command Window with Editor
• Thinking Command Window manages files
• Assuming Command Window creates GUIs

2. Which of the following is the correct way to display the value of variable x in the Command Window?

easy

A. disp(x)

B. print(x)

C. show(x)

D. echo x

Solution

1. Step 1: Recall MATLAB display functions

   In MATLAB, disp() is the standard function to display variable values in the Command Window.

2. Step 2: Check other options

   print() is for printing figures, show() and echo are not valid display commands for variables.

3. Final Answer:

   disp(x) -> Option A

4. Quick Check:

   Use disp() to display variable values [OK]

Hint: Use disp() to show variable values in Command Window [OK]

Common Mistakes:

• Using print() instead of disp()
• Trying non-existent functions like show()
• Using echo which is not a MATLAB command

3. What will be the output in the Command Window after running the following commands?

x = 5;
y = x + 3;
disp(y)

medium

A. x + 3

B. 53

C. Error

D. 8

Solution

1. Step 1: Calculate the value of y

   Variable x is assigned 5, then y = x + 3 means y = 5 + 3 = 8.

2. Step 2: Understand disp(y) output

   The disp(y) command prints the value of y, which is 8.

3. Final Answer:

   8 -> Option D

4. Quick Check:

   y = 5 + 3 = 8 [OK]

Hint: Add numbers before disp() to get output [OK]

Common Mistakes:

• Concatenating numbers as strings (53)
• Printing expression instead of value
• Expecting an error from correct syntax

4. Identify the error in the following MATLAB command typed in the Command Window:

disp('Hello World)

medium

A. Missing semicolon at end

B. disp function does not exist

C. Missing closing single quote

D. Incorrect use of parentheses

Solution

1. Step 1: Check string syntax

   The string starts with a single quote but does not have a matching closing single quote.

2. Step 2: Verify other syntax elements

   Semicolon is optional, disp is valid, and parentheses usage is correct except for the string quotes.

3. Final Answer:

   Missing closing single quote -> Option C

4. Quick Check:

   Strings need matching quotes [OK]

Hint: Always close quotes in strings [OK]

Common Mistakes:

• Ignoring missing quote errors
• Thinking semicolon is mandatory
• Assuming disp is undefined

5. You want to quickly test a small calculation and see the result without creating a script file. Which MATLAB Desktop feature should you use?

hard

A. Figure Window

B. Command Window

C. Workspace Browser

D. Editor

Solution

1. Step 1: Understand the purpose of each feature

   The Command Window lets you type commands and see results immediately without saving files.

2. Step 2: Compare with other features

   The Editor is for writing scripts, Workspace Browser shows variables, and Figure Window displays plots.

3. Final Answer:

   Command Window -> Option B

4. Quick Check:

   Quick tests = Command Window [OK]

Hint: Use Command Window for quick calculations [OK]

Common Mistakes:

• Trying to run quick code in Editor only
• Confusing Workspace Browser with command input
• Thinking Figure Window runs code