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Types of Functions in C

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Introduction

Functions are an important part of C programming. They help divide a program into smaller, manageable parts.

In C, functions are classified based on:

• Whether they take arguments
• Whether they return values

👉 Understanding types of functions helps you write better and more efficient programs.

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Categories of Functions

Functions in C are mainly divided into:

1. Library Functions
2. User-defined Functions

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1. Library Functions

These are predefined functions provided by C.

👉 Examples:

• printf()
• scanf()
• sqrt()
• strlen()

👉 You just use them — no need to define.

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2. User-defined Functions

Functions created by the programmer.

👉 These are further divided into 4 types:

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Types Based on Arguments & Return Value

Type	Arguments	Return Value
Type 1	No	No
Type 2	Yes	No
Type 3	No	Yes
Type 4	Yes	Yes

Type 1: No Arguments, No Return Value

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Example

#include <stdio.h>

void display() {
    printf("Hello from function");
}

int main() {
    display();
    return 0;
}

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Output

Hello from function

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Type 2: With Arguments, No Return Value

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Example

#include <stdio.h>

void add(int a, int b) {
    printf("Sum = %d", a + b);
}

int main() {
    add(5, 3);
    return 0;
}

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Output

Sum = 8

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Type 3: No Arguments, With Return Value

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Example

#include <stdio.h>

int getNumber() {
    return 10;
}

int main() {
    int num = getNumber();
    printf("Number = %d", num);
    return 0;
}

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Output

Number = 10

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Type 4: With Arguments, With Return Value

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Example

#include <stdio.h>

int multiply(int a, int b) {
    return a * b;
}

int main() {
    int result = multiply(4, 5);
    printf("Result = %d", result);
    return 0;
}

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Output

Result = 20

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Flow of Function Types

• Function call → Pass arguments (if any)
• Function executes
• Returns value (if any)

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Advantages of Using Functions

• ✔ Code reusability
• ✔ Modularity
• ✔ Easy debugging
• ✔ Better readability

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Common Mistakes

• ❌ Mismatch in arguments
• ❌ Wrong return type
• ❌ Missing return statement
• ❌ Incorrect function call

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Pro Tips

• ✔ Choose correct function type
• ✔ Use meaningful names
• ✔ Keep functions small
• ✔ Avoid unnecessary arguments

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Conclusion

Understanding types of functions helps you design better programs. It allows you to choose the right approach based on your needs.

Mastering functions is a key step toward advanced programming.

👉 This article is part of Dharani Tech Edu Hub — where learning programming is made simple and practical.