Simple Sample C Programs Using Functions

CASE STUDIES

(Programs Using Functions)

1. Write a user defined function that computes 'x' raised to the power of 'y'.

The problem 'x' raised to the power of 'y' means x^y, for this the input values are 'x' and 'y'.

Example: 10² Means 10*10 Evaluates 100

 /* Programs to computes 'x' raised to the power of 'y' */

#include <stdio.h>

#include <conio.h>

main()

{

int x,y;

int power(int, int);

clrscr();

printf("Enter x and y values....");

scanf("%d %d", &x, &y);

printf("%d to the power of %d is.. %f",x,y,power(x,y));

} /* main */

int power(int x, int y) /* Power is a function with arguments */

{

float p=1.0;

if(y >=0)

       while(y‒‒)

       p*=x;

else

       while(y++)

       p/=x;

return(p);

} /* power */

OUTPUT

Enter x and y values.... 10 2

10 to the power of 2 is.. 100

EXPLANATION: The above program calculates the value of 'x' to the power of y using the user defined function power(), which has two parameters of the type int and these can be taken from the input device.

2. Example for nesting of function.

Nesting of functions is the process of writing the function within another

Example: Calculate the ratio for the given x,y,z values using x/(y‒z).

* Program to calculate the ratio for the given x,y,z values */

#include <stdio.h>

#include <conio.h>

{

main()

/* Local definition */

int x,y,z,

float ratio (int, int, int);

/* Statements */

printf("Enter x,y,z values.....");

scanf("%d %d %d", &x, &y, &z);

printf("Ratio is..... %f\n", ratio(x,y,z));

} /* main */

float ratio(int x, int y, int z) /* ratio() is a function with arguments */

{

int diff(int, int);

if(diff(y,z))

          return(x/(y‒z));

else

          return(0);

} /* ratio() */

diff(int m,int n) /* diff() is a function with arguments */

{

if(m!=n)

      return(1);

else

       return(0);

} /* diff() */

OUTPUT

Enter x,y,z values... 10 10 5

Ratio is..... 2.000000

EXPLANATION: In the program the main function reads the values for x, y, z and calls the ratio() function to calculate x/(y‒z). The ratio can not be evaluated if (y‒z)=0, then the ratio function calls another function called diff() to find the difference between (y‒z) is zero or not.

3. Demonstration of Global variable

The multifunction program given below, demonstrates the global variable. The variable declared before the main() function is the global variable, the scope and availability of this variable is entire program.

/* Program to demonstration of global variable */

#include <stdio.h>

int a; /* global variable */

main()

{

a=39;

int f1();

int f2();

int f3();

printf("A..... %d\n", a);

printf("A..... %d\n", fl());

printf("A..... %d\n", f2());

printf("A..... %d\n",f3());

} /* main */

f1()

{

        a=a+10;

        return(a);

} /* fl */

f2()

{

        a=a+20;

        return(a);

} /* f2 */

f3()

{

        a=a+30;

        return(a);

} /* f3 */

OUTPUT

A.....39

A.....49

A.....69

A.....99

EXPLANATION: In the above program the variable a is declared as global declaration. This variable a is available any where in the program. The user‒defined functions f1(), f2(), and f(3) are accessed the a and executed the body of the statement then, it returns to the main program. Note that in all user‒defined functions the value of a does not change, hence it is global variable.