C FunctionsIn c, we can divide a large program into the basic building blocks known as function. The function contains the set of programming statements enclosed by {}. A function can be called multiple times to provide reusability and modularity to the C program. In other words, we can say that the collection of functions creates a program. The function is also known as procedureor subroutinein other programming languages. Advantage of functions in CThere are the following advantages of C functions.
Function AspectsThere are three aspects of a C function.
The syntax of creating function in c language is given below: Types of FunctionsThere are two types of functions in C programming:
Return ValueA C function may or may not return a value from the function. If you don't have to return any value from the function, use void for the return type. Let's see a simple example of C function that doesn't return any value from the function. Example without return value: If you want to return any value from the function, you need to use any data type such as int, long, char, etc. The return type depends on the value to be returned from the function. Let's see a simple example of C function that returns int value from the function. Example with return value: In the above example, we have to return 10 as a value, so the return type is int. If you want to return floatingpoint value (e.g., 10.2, 3.1, 54.5, etc), you need to use float as the return type of the method. Now, you need to call the function, to get the value of the function. Different aspects of function callingA 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.
Example for Function without argument and return valueExample 1 Output Hello Javatpoint Example 2 Output Going to calculate the sum of two numbers: Enter two numbers 10 24 The sum is 34 Example for Function without argument and with return valueExample 1 Output Going to calculate the sum of two numbers: Enter two numbers 10 24 The sum is 34 Example 2: program to calculate the area of the square Output Going to calculate the area of the square Enter the length of the side in meters: 10 The area of the square: 100.000000 Example for Function with argument and without return valueExample 1 Output Going to calculate the sum of two numbers: Enter two numbers 10 24 The sum is 34 Example 2: program to calculate the average of five numbers. Output Going to calculate the average of five numbers: Enter five numbers:10 20 30 40 50 The average of given five numbers : 30.000000 Example for Function with argument and with return valueExample 1 Output Going to calculate the sum of two numbers: Enter two numbers:10 20 The sum is : 30 Example 2: Program to check whether a number is even or odd Output Going to check whether a number is even or odd Enter the number: 100 The number is even C Library FunctionsLibrary functions are the inbuilt function in C that are grouped and placed at a common place called the library. Such functions are used to perform some specific operations. For example, printf is a library function used to print on the console. The library functions are created by the designers of compilers. All C standard library functions are defined inside the different header files saved with the extension .h. We need to include these header files in our program to make use of the library functions defined in such header files. For example, To use the library functions such as printf/scanf we need to include stdio.h in our program which is a header file that contains all the library functions regarding standard input/output. The list of mostly used header files is given in the following table.
Next TopicCall by value and call by reference in C

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