User-Defined Functions in MATLAB

🧩 User-Defined Functions in MATLAB

They help make programs modular, reusable, and easy to maintain.
MATLAB is developed by MathWorks.

🔹 What Is a User-Defined Function?

A user-defined function is a function written by the user (not built-in) that:

• Accepts input arguments

• Performs operations

• Returns output values

Functions are saved in .m files.

1️⃣ Basic Syntax of a Function

📌 The file name must be the same as the function name.

2️⃣ Example 1: Simple Function (Square of a Number)

🔸 Step 1: Create a file squareNum.m

🔸 Step 2: Call the Function

Output

3️⃣ Function with Multiple Inputs

🔸 Call

Output

4️⃣ Function with Multiple Outputs

🔸 Call

Output

5️⃣ Function Without Output

🔸 Call

Output

6️⃣ Function Without Input

7️⃣ Local Functions

A file can contain multiple functions, but:

• First function = main function

• Others = local functions

⚠️ Important Rules

• File name = function name

• function keyword is mandatory

• Variables inside functions are local

• Functions improve code reuse

🎯 Interview Questions: User-Defined Functions

🔹 Q1. What is a user-defined function in MATLAB?

Answer:
A function created by the user to perform specific operations.

🔹 Q2. What should be the file extension of a function file?

Answer:
.m

🔹 Q3. Can a function have multiple outputs?

Answer:
Yes, using square brackets [ ].

🔹 Q4. What is the scope of variables inside a function?

Answer:
Local to the function.

🔹 Q5. Can a function exist without input arguments?

Answer:
Yes.

🔹 Q6. Can a function exist without output arguments?

Answer:
Yes.

🔹 Q7. What is the first function in a file called?

Answer:
Main function.

✅ Summary

• User-defined functions improve modularity

• Support inputs and outputs

• Saved in .m files

• Essential for structured MATLAB programs