21 Nov C – Functions
A function in C Language is an organized block of reusable code, which avoids repeating the tasks repeatedly. If you want to do a task repeatedly in a code, just make a function, set the task in it, and call the function multiple times whenever you need it.
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:
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void demoFunction() { // write the code } |
A function in C language gets executed when it is called:
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demoFunction(); |
Let us now see an example to create a function:
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#include <stdio.h> // Demo function void demoFunction() { printf("This is a demo function.\n"); } int main() { // Calling the function demoFunction(); return 0; } |
Output
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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:
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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:
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void demoFunction(); |
The following is the function definition:
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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:
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#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
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This is a demo function. |
Function Parameters
Set the parameters in a C function after the name of the function. For example:
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void demoFunction(int rank) { } |
To call a function with a parameter, set the value of the variable while calling, for example:
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demoFunction(5) |
Therefore, we have passed the rank with the value 5 while calling above.
Let us now see an example:
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#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
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Rank = 5 |
Multiple Parameters
We can also set more than one parameter in a function. For example:
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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:
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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:
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#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
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Player = Amit Rank = 1 Points = 100 Player = David Rank = 2 Points = 90 |
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