C Useful programs

Accessing Array Elements

#include 

#include

int main ()

{

   int n[ 10 ];

   int i,j;

   for ( i = 0; i < 10; i++ )

   {

      n[ i ] = i + 100; 

   }

      for (j = 0; j < 10; j++ )

   {

      printf("Element[%d] = %d\n", j, n[j] );

   }

    return 0;

}

C using Strings program

#include 

#include

#include 

int main ()

{

   char str1[12] = "Hello";

   char str2[12] = "World";

   char str3[12];

   int  len ;

   strcpy(str3, str1);

   printf("strcpy( str3, str1) :  %s\n", str3 );

   strcat( str1, str2);

   printf("strcat( str1, str2):   %s\n", str1 );

   len = strlen(str1);

   printf("strlen(str1) :  %d\n", len );

   return 0;

}

Calling Functions program

#include 

#include 

int max(int num1, int num2);

int main ()

{

   int a = 100;

   int b = 200;

   int ret;

   ret = max(a, b);

   printf( "Max value is : %d\n", ret );

   return 0;

}

int max(int num1, int num2) 

{

   int result;

    if (num1 > num2)

      result = num1;

   else

      result = num2;

    return result; 

}

Variable Arguments

#include 

#include

#include 

double average(int num,...)

{

    va_list valist;

    double sum = 0.0;

    int i;

    va_start(valist, num);

    for (i = 0; i < num; i++)

    {

       sum += va_arg(valist, int);

    }

     va_end(valist);

    return sum/num;

}

int main()

{

   printf("Average of 2, 3, 4, 5 = %f\n", average(4, 2,3,4,5));

   printf("Average of 5, 10, 15 = %f\n", average(3, 5,10,15));

}

Allocating Memory Dynamically

#include 

#include

#include 

#include 

int main()

{

   char name[100];

   char *description;

   strcpy(name, "Zara Ali");

   description = malloc( 200 * sizeof(char) );

   if( description == NULL )

   {

      fprintf(stderr, "Error - unable to allocate required memory\n");

   }

   else

   {

      strcpy( description, "Zara ali a DPS student in class 10th");

   }

   printf("Name = %s\n", name );

   printf("Description: %s\n", description );

}

Resizing and Releasing Memory

#include 

#include

#include 

#include 

int main()

{

   char name[100];

   char *description;

   strcpy(name, "Zara Ali");

   description = malloc( 30 * sizeof(char) );

   if( description == NULL )

   {

      fprintf(stderr, "Error - unable to allocate required memory\n");

   }

   else

   {

      strcpy( description, "Zara ali a DPS student.");

   }

   description = realloc( description, 100 * sizeof(char) );

   if( description == NULL )

   {

      fprintf(stderr, "Error - unable to allocate required memory\n");

   }

   else

   {

      strcat( description, "She is in class 10th");

   }

   printf("Name = %s\n", name );

   printf("Description: %s\n", description );

   free(description);

}