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Functions in C, In 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, procedure or subroutine in other programming languages., Advantages of Function, There are the following advantages of C functions., •, •, •, •, •, , By using functions, we can avoid rewriting same logic/code again and again in a, program., We can call C functions any number of times in a program and from any place in a, program., We can track a large C program easily when it is divided into multiple functions., Reusability is the main achievement of C functions., However, Function calling is always a overhead in a C program., , Function Aspects, There are three aspects of a C function., •, •, , •, , Function declaration A function must be declared globally in a c program to tell the, compiler about the function name, function parameters, and return type., Function call Function can be called from anywhere in the program. The parameter list, must not differ in function calling and function declaration. We must pass the same, number of functions as it is declared in the function declaration., Function definition It contains the actual statements which are to be executed. It is, the most important aspect to which the control comes when the function is called., Here, we must notice that only one value can be returned from the function., , Syntax for function declaration:, Return_type function name(data_type parameter...), {, //code to be executed, }, Types of Function, There are two types of functions in C programming:, 1. Library Functions: are the functions which are declared in the C header files such as, scanf (), printf (), gets (), puts (), ceil (), floor () etc., 2. User-defined functions: are the functions which are created by the C programmer, so, that he/she can use it many times. It reduces the complexity of a big program and, optimizes the code.

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Return Value, A 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., Example without return value:, void hello (), {, printf ("hello c");, }, 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., Example with return value:, int get (), {, return 10;, }, In the above example, we have to return 10 as a value, so the return type is int. If you want, to return floating-point value (e.g., 10.2, 3.1, 54.5, etc), you need to use float as the return, type of the method., float get (), {, return 10.2;, }, Different Aspects of function calling:, 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, , function without arguments and without return value, Example 1:, #include<stdio.h>, void printName ();, void main (), {

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printf ("Hello ");, printName ();, }, void printName (), {, printf("Java point");, }, , Example 2:, #include<stdio.h>, void sum ();, void main (), {, printf ("\nGoing to calculate the sum of two numbers:");, sum ();, }, void sum (), {, int a,b;, printf ("\nEnter two numbers");, scanf ("%d %d”, &a, &b);, printf ("The sum is %d”, a+b);, }, function without arguments and with return value, Example 1:, #include<stdio.h>, int sum ();, void main (), {, int result;, printf ("\nGoing to calculate the sum of two numbers:");, result = sum ();, printf ("%d”, result);, }, int sum (), {, int a,b;, printf ("\nEnter two numbers");, scanf ("%d %d”, &a, &b);, return a+b;, }

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Example2: To calculate the area of square, #include<stdio.h>, int sum ();, void main (), {, printf ("Going to calculate the area of the square\n");, float area = square ();, printf ("The area of the square: %f\n",area);, }, int square (), {, float side;, printf ("Enter the length of the side in meters: ");, scanf("%f",&side);, return side * side;, }, function with arguments and without return value, Example 1:, #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);, }, Example 2: To calculate the average of five number, #include<stdio.h>, void average (int, int, int, int, int);, void main (), {, int a, b, c, d, e;, printf ("\nGoing to calculate the average of five numbers:");, printf ("\nEnter five numbers:");, scanf ("%d %d %d %d %d”, &a, &b, &c, &d, &e);

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average (a, b, c, d, e);, }, void average (int a, int b, int c, int d, int e), {, float avg;, avg = (a+b+c+d+e)/5;, printf ("The average of given five numbers: %f”, avg);, }, , function with arguments and with return value, Example 1:, #include<stdio.h>, int 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);, result = sum (a, b);, printf ("\nThe sum is: %d”, result);, }, int sum (int a, int b), {, return a+b;, }, Example 2: To check whether a number is even or not, #include<stdio.h>, int even_odd(int);, void main (), {, int n, flag=0;, printf ("\nGoing to check whether a number is even or odd");, printf ("\nEnter the number: ");, scanf ("%d”, &n);, flag = even_odd(n);, if (flag == 0), {, printf ("\nThe number is odd");, }, else, {, printf ("\nThe number is even");

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}, }, int even_odd (int n), {, if (n%2 == 0), {, return 1;, }, else, {, return 0;, }, }, Library Functions In C, Library 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., , 1 stdio.h, , This is a standard input/output header file. It contains all the library functions, regarding standard input/output., , 2 conio.h This is a console input/output header file., 3 string.h It contains all string related library functions like gets(), puts(),etc., 4 stdlib.h, , This header file contains all the general library functions like malloc(), calloc(),, exit(), etc., , 5 math.h, , This header file contains all the math operations related functions like sqrt(),, pow(), etc., , 6 time.h, , This header file contains all the time-related functions., , 7 ctype.h This header file contains all character handling functions., 8 stdarg.h Variable argument functions are defined in this header file., 9 signal.h All the signal handling functions are defined in this header file., 10 setjmp.h This file contains all the jump functions., 11 locale.h This file contains locale functions., 12 errno.h This file contains error handling functions., 13 assert.h This file contains diagnostics functions.