Script files and editor in MATLAB - Step-by-Step Execution

Concept Flow - Script files and editor

Open Editor

↓

Write Script Code

↓

Save as .m file

↓

Run Script

↓

View Output in Command Window

↓

Edit and Repeat if needed

This flow shows how you open the editor, write and save a script file, run it, and see the output.

Execution Sample

MATLAB

a = 5;
b = 3;
c = a + b;
disp(c);

This script adds two numbers and displays the result.

Execution Table

Step	Code Line	Action	Variable State	Output
1	a = 5;	Assign 5 to a	a=5
2	b = 3;	Assign 3 to b	a=5, b=3
3	c = a + b;	Add a and b, assign to c	a=5, b=3, c=8
4	disp(c);	Display value of c	a=5, b=3, c=8	8
5	End of script	Script finishes running	a=5, b=3, c=8

💡 Script ends after last line is executed.

Variable Tracker

Variable	Start	After Step 1	After Step 2	After Step 3	Final
a	undefined	5	5	5	5
b	undefined	undefined	3	3	3
c	undefined	undefined	undefined	8	8

Key Moments - 2 Insights

Why does the output only show after disp(c) and not after assigning c = a + b?

Because MATLAB only shows output when you explicitly ask it to display, like with disp(). Assignments do not print values automatically (see execution_table step 3 vs step 4).

What happens if you forget to save the script before running?

The editor will run the last saved version, so changes not saved won't run. Always save your .m file before running (concept_flow step 3).

Visual Quiz - 3 Questions

Look at the execution table, what is the value of variable 'c' after step 3?

A 8

B 5

C 3

D undefined

💡 Hint

Check the 'Variable State' column in row for step 3.

At which step does the script display output to the command window?

A Step 2

B Step 4

C Step 3

D Step 5

💡 Hint

Look for the 'Output' column showing a value.

If you change 'disp(c);' to 'disp(a);', what will be displayed at step 4?

A 3

B 8

C 5

D Error

💡 Hint

Refer to variable_tracker for value of 'a' after step 1.

Concept Snapshot

Script files in MATLAB are saved as .m files.
Use the Editor to write and save your code.
Run scripts to execute all lines in order.
Use disp() to show output in Command Window.
Save changes before running to see updates.

Full Transcript

In MATLAB, you write code in the Editor and save it as a script file with a .m extension. When you run the script, MATLAB executes each line in order. Variables get assigned values step by step. To see output, you use the disp() function. The Editor helps you write, save, and run scripts easily. Remember to save your script before running it so your latest changes take effect.

Practice

1. What is the main purpose of a script file in MATLAB?

easy

A. To create graphical user interfaces

B. To save and run a group of commands together

C. To store variables permanently

D. To compile MATLAB code into an executable

Solution

1. Step 1: Understand what script files do

   Script files contain a sequence of MATLAB commands saved in a file to run together.

2. Step 2: Compare options with script file purpose

   Only To save and run a group of commands together describes saving and running commands together, which is the main use of scripts.

3. Final Answer:

   To save and run a group of commands together -> Option B

4. Quick Check:

   Script files = save and run commands [OK]

Hint: Scripts group commands to run all at once [OK]

Common Mistakes:

• Confusing scripts with functions
• Thinking scripts store variables permanently
• Assuming scripts compile code

2. Which of the following is the correct way to save a script file in MATLAB Editor?

easy

A. Click File > Save or press Ctrl+S

B. Type save script in the command window

C. Right-click the command window and select Save

D. Use the command saveas('filename') in the script

Solution

1. Step 1: Identify how to save files in MATLAB Editor

   The Editor uses standard save options like File menu or Ctrl+S shortcut.

2. Step 2: Evaluate each option

   Only Click File > Save or press Ctrl+S correctly describes saving via Editor menu or shortcut. Others are incorrect or commands for different purposes.

3. Final Answer:

   Click File > Save or press Ctrl+S -> Option A

4. Quick Check:

   Save script = File menu or Ctrl+S [OK]

Hint: Use File menu or Ctrl+S to save scripts [OK]

Common Mistakes:

• Trying to save scripts from command window
• Using saveas command incorrectly
• Right-clicking command window instead of Editor

3. What will be the output when running this script in MATLAB Editor?

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

medium

A. 8

B. 53

C. x + y

D. Error: Undefined variable

Solution

1. Step 1: Understand the script commands

   Variables x and y are assigned 5 and 3, then z is sum of x and y.

2. Step 2: Calculate the value of z and output

   z = 5 + 3 = 8, disp(z) prints 8 to the command window.

3. Final Answer:

   8 -> Option A

4. Quick Check:

   5 + 3 = 8 output [OK]

Hint: Add variables then display result [OK]

Common Mistakes:

• Concatenating numbers as strings
• Expecting variable names printed
• Assuming error without variable initialization

4. Identify the error in this MATLAB script:

for i = 1:3
  disp(i)
endd

medium

A. disp function used incorrectly

B. Missing semicolon after disp(i)

C. Loop variable i is not defined

D. Incorrect end keyword spelling

Solution

1. Step 1: Check the loop syntax

   The for loop uses 'endd' instead of 'end' to close the loop.

2. Step 2: Identify the syntax error

   MATLAB requires 'end' keyword exactly; 'endd' causes a syntax error.

3. Final Answer:

   Incorrect end keyword spelling -> Option D

4. Quick Check:

   Loop ends with 'end' keyword [OK]

Hint: Use exact 'end' to close loops [OK]

Common Mistakes:

• Typing 'endd' instead of 'end'
• Forgetting to close loops
• Adding unnecessary semicolons

5. You want to create a script that calculates the average of numbers stored in a vector data. Which script structure correctly computes and displays the average?

hard

A. avg = mean(data)
disp(total);

B. for i = 1:length(data)
avg = data(i) / length(data);
end
disp(avg);

C. total = sum(data);
count = length(data);
avg = total / count;
disp(avg);

D. avg = sum(data) * length(data);
disp(avg);

Solution

1. Step 1: Understand how to calculate average

   Average = sum of elements divided by number of elements.

2. Step 2: Check each script option

   total = sum(data);
   count = length(data);
   avg = total / count;
   disp(avg);

   correctly sums data, counts elements, divides, then displays average. Others have errors: A displays undefined total, C overwrites avg incorrectly in loop, D multiplies instead of dividing.

3. Final Answer:

   total = sum(data); count = length(data); avg = total / count; disp(avg); -> Option C

4. Quick Check:

   Average = sum / count [OK]

Hint: Average = sum divided by count, then display [OK]

Common Mistakes:

• Using mean without displaying correct variable
• Calculating average inside loop incorrectly
• Multiplying sum by length instead of dividing