21 Nov C – Functions
A function in C Language is an organized block of reusable code, which avoids repeating tasks. If you want to do a task repeatedly in code, just make a function, set the task in it, and call the function multiple times whenever you need it.
Before moving further, we’ve prepared a video tutorial to understand what functions are in C:
Video: Functions in C
Video: Functions in C (Hindi)
In this lesson, we will see:
- How to create and call a function
- Create a function by separating the function definition and declaration
- Create a Function with a parameter
- Create a Function with multiple parameters
Create and call a Function (Function Declaration & Definition)
To create a function in C language, set the name of the function followed by parentheses. Here, void is the return type. Use void if the function does not return a value:
void demoFunction() {
// write the code
}
A function in C language gets executed when it is called:
demoFunction();
Let us now see an example to create a function:
#include <stdio.h>
// Demo function
void demoFunction() {
printf("This is a demo function.\n");
}
int main() {
// Calling the function
demoFunction();
return 0;
}
Output
This is a demo function.
Function Declaration and Definition (separate)
In the above example, we saw how to create and call a function. We defined and declared the function as well:
void demoFunction() { // function declaration
// function body i.e. the definition
}
As shown above, a function has two parts:
- Function Declaration
- Function Definition
The following is the function declaration:
void demoFunction();
The following is the function definition:
void demoFunction() {
printf("This is a demo function.\n");
}
We can also write the above function by separating function definition and declaration. Let us see an example:
#include <stdio.h>
// Function Declaration
void demoFunction();
int main() {
// Calling the function
demoFunction();
return 0;
}
// Function Definition
void demoFunction() {
printf("This is a demo function.\n");
}
Output
This is a demo function.
Function Parameters
Set the parameters in a C function after the name of the function. For example:
void demoFunction(int rank) { }
To call a function with a parameter, set the value of the variable while calling, for example:
demoFunction(5)
Therefore, we have passed the rank with the value 5 while calling above.
Let us now see an example:
#include <stdio.h>
// Function with a parameter
void detailsFunc(int rank) {
printf("Rank = %d",rank);
}
int main() {
// Calling the function
detailsFunc(5);
return 0;
}
Output
Rank = 5
Multiple Parameters
We can also set more than one parameter in a function. For example:
void demoFunction(char player[], int rank, int points) { }
To call a function with multiple parameters, set the value of the variable while calling, for example:
demoFunction("Amit", 1, 100)
We have passed the following multiple parameters while calling above:
- player: Amit
- rank: 1
- points: 100
Let us now see an example:
#include <stdio.h>
// Function with multiple parameters
void detailsFunc(char player[], int rank, int points) {
printf("Player = %s",player);
printf("\nRank = %d",rank);
printf("\nPoints = %d\n\n",points);
}
int main() {
// Calling the function
detailsFunc("Amit", 1, 100);
detailsFunc("David", 2, 90);
return 0;
}
Output
Player = Amit Rank = 1 Points = 100 Player = David Rank = 2 Points = 90
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