C Functions Definition Types Syntax And Examples

Here, we will explore the process of defining and declaring functions in the C programming language.

Function Declaration

In the realm of C programming, a function declaration provides information regarding the function's name, parameters, and return type. This enables the compiler to utilize the details prior to the function being fully defined. By doing so, it guarantees the validity and type safety of function calls, regardless of when the function is actually defined within the program.

Syntax of Function Declaration

It has the following syntax:

return_type function_name(parameter_list);

In this syntax;

• ✅ return_type: It represents the return type, such as int, char, double, string, void, etc.
• ✅ function_name: It is used to represent the name of the function.
• ✅ parameter_list: It is used to represent the name of the parameter.

Function Declaration Example

Let's consider an example to demonstrate how a function is declared in the C programming language.

int add(int a, int b);  // Declaring a function that returns an int and takes two int arguments

Function Definition

In the realm of C programming, a function definition encapsulates the precise functionality of the function, containing the code block responsible for executing a particular task. This definition communicates to the compiler the actions the function undertakes upon invocation. In contrast to a function declaration, the definition encompasses the actual implementation details.

int addition(int a, int b)   

{   

    return a + b;  

}

Function Call

In the C programming language, invoking a function involves specifying the function's name and required parameters. Upon calling the function, the program flow transitions to the code enclosed within the function's definition, and subsequently, the output is generated. This practice promotes the reuse of code and facilitates modular programming in C, leading to enhanced code organization.

Syntax for Function Call

It has the following syntax:

function_name(actual_arguments);

Function Call Example in C

Let's consider an example to demonstrate the process of making function calls in the C programming language.

int result = add(5, 10);  // Calling the function and storing result

Simple Function Example in C

Let's consider an example to demonstrate a function in the C programming language.

Example

#include <stdio.h>



// Function Declaration

int multiply(int, int);



int main() {   //main function

    int result;



    // Calling the add function

    result = multiply(4, 5);



    printf("The Multiplication of Numbers is: %d\n", result);

    return 0;

}



// Function Definition

int multiply(int a, int b) {

    return a * b;

}

Output:

The Multiplication of Numbers is: 20

Explanation:

In this instance, we showcase the implementation of a function declaration, definition, and invocation. We've selected the multiply function, which accepts two integer parameters, computes their product, and then outputs the outcome. Subsequently, the main function invokes the custom function and displays the calculated product.

Return type of functions in C

A C function's return type specifies the data type of the value that will be returned to the calling function upon completion. It provides the compiler with information regarding the data types such as char, float, and int that the function will produce.

Types of Functions in C

There are primarily two categories of functions in C programming. These include:

1) Library Functions

Library functions in C refer to the built-in functions grouped together in a centralized location known as the library. These functions are designed for specific tasks, such as the function printf which is employed for displaying output on the console. Compiler designers are responsible for developing these library functions, and they are stored within various header files with the .h extension.

We must incorporate these header files into our code to utilize the library functions specified in them. For instance, to utilize functions like printf/scanf, we must include stdio.h in our program. This header file encompasses all the library functions related to standard input/output operations. Library Functions refer to the predefined functions primarily declared in C header files, such as scanf, printf, gets, puts, ceil, floor, and more.

The table presents a compilation of commonly utilized header files.

Key Features of Library Functions

Several key features of the library functions in C programming are as follows:

• ✅ The C Standard Library's library functions are more effective because they are already written and compiled. It helps to ensure their independence from any platform, extensive testing, and optimal performance.
• ✅ Pre-compiled solutions for fundamental operations, such as algebra, input/output formatting, and even string manipulation offer immense value to programmers by saving time and effort.
• ✅ In regard to string manipulation, library files had specific rules that defined what should be included at the beginning of each code, such as <stdio.h>, <math.h>, or <string.h>.
• ✅ Examples of Use: Examples of input/output functions are scanf and printf. Use the strlen and strcpy function to handle strings. In mathematics, the functions ceil and floor are used to round integers.
• ✅ Examples of input/output functions are scanf and printf.
• ✅ Use the strlen and strcpy function to handle strings.
• ✅ In mathematics, the functions ceil and floor are used to round integers.

A basic library function in C can be created by utilizing the sqrt function for calculating square roots.

Let's consider an example to demonstrate the library function in C by utilizing the sqrt function.

Example

#include <stdio.h>

#include <math.h>  // Required for sqrt()



int main() {  //main function

    double num = 169.0;

    double result;



    // Using the sqrt() library function

    result = sqrt(num);



    printf("The square root of %.2f is %.2f\n", num, result);

    return 0;

}

Output:

The square root of 169.00 is 13.00

Explanation:

In this instance, we showcase the application of the library function sqrt from the math.h header to compute the square root of a specific value. Following this calculation, the variable num is assigned a value of 169.0, and applying sqrt(num) yields its corresponding square root, which is subsequently displayed using the printf function.

2) User Defined Functions in C

In the realm of C programming, custom functions are functions crafted by the C developer to be reused multiple times by the user. This practice serves to simplify intricate programs and enhance the efficiency of the codebase.

Key Features of User Defined Functions in C

Several key features of user-defined functions in C programming are as follows:

• ✅ Logic encapsulation through user-defined functions helps improve modularity and system scalability because code blocks that have similarities can be stored in a single name container.
• ✅ There is less risk for errors, which helps to improve maintainability because changes in logic can be made containing a single function instead of multiple parts throughout the code.
• ✅ A function's usefulness and variety may be enhanced by enabling it to accept parameters and return values.
• ✅ Controlling the function's name, scope, and behavior is useful for avoiding conflicts and tailoring logic to specific requirements.
• ✅ "Recursiveness" is the capacity of user-defined functions to call themselves. This capacity can be used to solve tree traversal, Fibonacci, and factorial challenges.

User Defined Functions Example in C

Let's consider an example to demonstrate the user-defined function in the C programming language.

Example

#include <stdio.h>



// User-defined function declaration

void logic practice();



int main() {

    // Function call

    logic practice();

    return 0;

}



// User-defined function definition

void logic practice() {

    printf("Hello! Welcome to the Logic Practice.\n");

}

Output:

Hello! Welcome to the Logic Practice.

Explanation:

In this instance, we create a custom function called logic practice which outputs a greeting message. Subsequently, this function is defined prior to the main function, invoked within the main function, and defined thereafter. Upon execution, it presents the desired output.

Key differences between library functions and User Defined functions

Several variances between library functions and user-defined functions in C are outlined below:

Types of User Defined Function in C

A function may or may not accept any argument. It may or may not return any value. Based on these facts, there are four different aspects of function calls.

• ✅ function without arguments and without return value
• ✅ function without arguments and with return value
• ✅ function with arguments and without return value
• ✅ function with arguments and with return value

Now, we will examine each of these custom functions individually in the C programming language.

A function that does not require any arguments and does not return any value is known as a void function.

In C programming, this kind of function does not require any input parameters or return any values. It is commonly used when the function completes a task that does not require additional data or results to be sent back to the calling function. This type of function operates as a self-contained logic unit. Typically invoked from the main function, these functions can display messages or execute predetermined operations.

A function with no parameters and no return value is demonstrated in the following example:

Let's consider an example to demonstrate a function in C without parameters and without a return value.

Example

#include<stdio.h>  

void printName();  

void main ()  

{  

    printf("Hello ");  

    printName();  

}  

void printName()  

{  

    printf("Logic Practice");  

}

Output:

Hello Logic Practice

Explanation:

In this instance, we showcase a custom function named displayFullName responsible for outputting "Algorithm Exercise". Within the primary function, the initial output is "Greetings ", and subsequently, the displayFullName function is invoked, leading to the final output: Greetings Algorithm Exercise.

Function without arguments and with return value

In C programming, this method does not accept any parameters. Additionally, it sends a result back to the calling function.

Define a function that does not require any arguments but returns a specific value upon execution.

Let's consider a scenario to demonstrate a function in C without parameters and without a return value.

Example

#include <stdio.h>



int getNumber() {  // No arguments, but returns an int

    return 100;

}



int main() {

    int num = getNumber();  // Function call

    printf("Returned number is: %d\n", num);

    return 0;

}

Output:

Returned number is: 100

Explanation:

In this instance, we establish a function named fetchValue that accepts no parameters and gives back the number 100 as an integer. Within the primary function, the outcome is captured in the variable value and then displayed.

Function with arguments and without return value

In C programming, this kind of function takes in parameters but does not give back a value. It carries out multiple tasks using the provided inputs and might directly show the outcome. These functions are valuable when a task needs to be carried out using inputs without returning a result to the calling function.

Function with parameters and no return value Example

Let's consider an example to demonstrate a Function with parameters and no return value in the C programming language.

Example

#include<stdio.h>  

void sum(int, int);  

void main()  

{  

    int a,b,result;   

    printf("\nGoing to calculate the sum of two numbers:");  

    printf("\nEnter two numbers:");  

    scanf("%d %d",&a,&b);  

    sum(a,b);  

}  

void sum(int a, int b)  

{  

    printf("\nThe sum is %d",a+b);      

}

Output:

Going to calculate the sum of two numbers:

Enter two numbers:12 34

The sum is 46

Explanation:

In this illustration, a function named sum(int, int) is established to accept two parameters and output their total. Within the main function, the user inputs two numerical values that are then sent to the aforementioned function. The computation is performed by the function and the outcome is promptly exhibited without being returned.

Function without arguments and with return value

In the realm of C programming, this design is widely favored and flexible. Functions not only receive inputs but also yield outputs. Functions that handle input data and return results to the calling code excel in this aspect. Emphasizing modularity and reusability, it forms the basis of structured programming in the C language.

Create a function that does not require any arguments but returns a specific value upon execution.

Let's consider a scenario to demonstrate a function in C without parameters but with a return value.

Example

#include <stdio.h>



int multiply(int a, int b) {  // Takes arguments and returns a value

    return a * b;

}



int main() {

    int result = multiply(5, 6);  // Function call

    printf("Product: %d\n", result);

    return 0;

}

Output:

Product: 30

Explanation:

In this illustration, the computer computes the multiplication of two integers using the user-defined function multiply. Following this, the function takes two integers as inputs, processes them, and outputs their product. Within the main function, the function is invoked with 5 and 6 as parameters, and the result is saved in the variable named result.

Advantage of functions in C

Several advantages of functions in C are as follows:

• ✅ Functions do away with code duplication. We write the logic once and use it wherever needed.
• ✅ Code becomes simpler and more modular due to the ability of calling a function multiple times from various parts of a program.
• ✅ It becomes much easier to manage, test, and understand when a large software application is broken into smaller pieces.
• ✅ A major benefit of this is the ability to reuse code and employ the same function in multiple systems without rebuilding it each time.
• ✅ Remember that there are costs involved in calling a function, i.e., supplying parameters and making a jump to the memory address of the function. It can have a slight effect on performance where quick response applications are concerned.

Disadvantages of functions in C

Several disadvantages of functions in C are as follows:

• ✅ Function call overhead is the extra time and memory needed for argument transmission and control transfer.
• ✅ Data encapsulation is not present. Data cannot be concealed like OOP does; global variables could lead to issues.
• ✅ Code that is hard to read can be caused by the use of too many tiny functions.
• ✅ Due to the difficulty of tracking errors across multiple procedures, debugging becomes more challenging.
• ✅ The same function name cannot be used with different arguments because there is no function overloading.
• ✅ Since there are no built-in parameters, all of them must be specified individually.
• ✅ Tight coupling means modifying one function that could affect other functions in large programs.

Conclusion

In summary, functions play a crucial role in C programming by providing structure, reusability, and modularity to programs. By dividing large programs into smaller functions, developers can prevent redundant code and enhance the efficiency and manageability of the codebase. The ability to invoke functions at any point in the program offers flexibility and enhances the overall flow of control.

In C programming, functions play a vital role as fundamental components, offering advantages such as enhanced structuring, code reusability, and easier management of large-scale projects. While invoking functions may introduce some additional processing, the benefits they bring far surpass the slight impact on performance. By understanding and incorporating functions, developers can create efficient and scalable C programs.