Curriculum

C basic

C Home

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C Introduction

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C Get Started

0/1

C Syntax

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C Output

0/2

C Comments

0/1

C Variables

0/6

C Data Types

0/7

C Constants

0/1

C Operators

0/1

C Booleans

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C If ... Else

0/5

C Switch

0/1

C Break and Continue

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C While Loop

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C For Loop

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C Arrays

0/4

C Strings

0/3

C User Input

0/1

C Memory Address

0/1

C Pointers

0/2

C Functions

0/5

C Files

0/3

C Structures

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C Enums

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C Memory

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Text lesson

C Function Declaration

Function Declaration and Definition

You’ve just learned from the preceding chapters how to create and invoke a function as follows:

Example

// Create a function
void myFunction() {
printf(“I just got executed!”);
}

int main() {
myFunction(); // call the function
return 0;
}

A function comprises two components:

Declaration: Includes the function’s name, return type, and parameters (if any).
Definition: Encompasses the body of the function, containing the code to be executed.

void myFunction() { // declaration
// the body of the function (definition)
}

For enhanced code optimization, it’s advisable to segregate the declaration and definition of functions. It’s a common practice in C programming to place function declarations above the main() function and function definitions below it. This promotes better code organization and readability:

Example

// Function declaration
void myFunction();

// The main method
int main() {
myFunction(); // call the function
return 0;
}

// Function definition
void myFunction() {
printf(“I just got executed!”);
}

Another Example

If we refer back to the example provided in the preceding chapter regarding function parameters and return values:

Example

int myFunction(int x, int y) {
return x + y;
}

int main() {
int result = myFunction(5, 3);
printf(“Result is = %d”, result);
return 0;
}
// Outputs 8 (5 + 3)

Writing it in the following manner is considered good practice:

Example

// Function declaration
int myFunction(int, int);

// The main method
int main() {
int result = myFunction(5, 3); // call the function
printf(“Result is = %d”, result);
return 0;
}

// Function definition
int myFunction(int x, int y) {
return x + y;
}